Document:

<PAGE>

                                                                   EXHIBIT 10.26
                       ASSIGNMENT AND ASSUMPTION OF LEASE

     THIS ASSIGNMENT AND ASSUMPTION OF LEASE (this "Assignment"), made as of the
5th day of April, 2000, between ZD Inc., a Delaware corporation, having an
office at 28 East 28th Street, New York, New York 10016 ("Assignor"), and
Ziff Davis Publishing Inc., a Delaware corporation, having an office c/o Willis
Stein & Partners II, L.P., 227 West Monroe Street, Chicago, Illinois 60606
("Assignee").

                              W I T N E S S E T H:

     WHEREAS, by that certain Lease dated as of January 15, 1998, between 63
Madison Associates, L.P. ("Landlord"), as landlord, and Ziff-Davis Inc. n/k/a ZD
Inc., as tenant, as amended by letter agreement dated September 23, 1999 between
Landlord and Assignor (collectively, the "Lease"), Landlord is leasing to
Assignor Concourse Level "B-2" and the entire 8th, 9th, 10th, 11th, 12th, 13th,
14th and 15th floors (collectively, the "Premises") of the building (the
"Building") known as 63 Madison Avenue, New York, New York 10016 as more
particularly described on Schedule 1 annexed hereto;

     WHEREAS, by that certain Sublease dated March 16, 2000 between Assignor, as
sublandlord, and Softbank Inc., as subtenant (the "15th Floor Sublease"),
Assignor is subleasing to Softbank Inc. the entire 15th floor of the Building on
the terms and conditions described therein;

     WHEREAS, by that certain Sublease dated March 10, 2000 between Assignor, as
sublandlord, and Ziff-Davis Inc., as subtenant (the "10th Floor Sublease" and,
collectively with the 15th Floor Sublease, the "Subleases"), Assignor is
subleasing to Ziff-Davis, Inc. the entire 10th floor of the Building on the
terms and conditions contained therein; and

     WHEREAS, Assignor desires to assign and transfer to Assignee (i) Assignor's
right, title and interest in and to the Lease subject to the Subleases and (ii)
Assignor's right, title and interest in and to the Subleases; and Assignee
desires to accept such assignment and transfer upon the terms and conditions
hereinafter set forth.

     NOW, THEREFORE, in consideration of the mutual covenants herein contained,
it is mutually agreed as follows:

     1. Assignment by Assignor. Assignor hereby assigns and transfers to
Assignee (a) all of Assignor's right, title and interest in and to the Lease
subject to the Subleases and (b) all of Assignor's right, title and interest in
and to the Subleases, in each case subject to the terms and conditions
hereinafter set forth.

     2. Effective Date of Assignment. This Assignment shall take effect on the
"Closing Date" specified in that certain Purchase Agreement dated as of December
6, 1999 between Assignor and Assignee (the "Purchase Agreement"), and Assignor
shall give possession of the Premises to Assignee on that date (the "Assignment
Date").

After recording, this Assignment should be returned to:

Roberto S. Miceli, Esq.
---------------------------------------
Kirkland & Ellis
---------------------------------------
200 East Randolph Drive
---------------------------------------
Chicago, IL 60601
---------------------------------------

     3. Acceptance and Assumption by Assignee. Assignee hereby accepts the
assignment and transfer of Assignor's right, title and interest in and to the
Lease subject to the
<PAGE>

Subleases and Assignor's right, title and interest in and to the Subleases and
promises to pay all rent and additional rent under the Lease and to faithfully
perform all covenants, stipulations, agreements and obligations under the Lease
and the Subleases accruing on or after the Assignment Date or otherwise
attributable to the period commencing on the Assignment Date and continuing
thereafter.

     4. Notices. Except as otherwise specifically provided herein, any notice,
statement, demand, consent, approval, advice or other communication required or
permitted to be given, rendered or made by either party to the other, pursuant
to this Assignment or pursuant to any applicable law or requirement of public
authority (collectively, "communications") shall be in writing and shall be
deemed to have been properly given, rendered or made only if sent by personal
delivery, or registered or certified mail, return receipt requested, posted in a
United States post office station in the continental United States, or by a
nationally recognized overnight courier, in each case addressed (i) to Assignor
at its address first above written, Attention: President and (ii) to Assignee,
at its address first above written, Attention: President. A copy of each
communication to Assignor shall also be sent to Clifford Chance Rogers & Wells
LLP, 200 Park Avenue, New York, New York 10166, Attention: Joanne Feil, Esq. All
such communications shall be deemed to have been given, rendered or made when
delivered on the date such communication is actually received as evidenced by a
written receipt therefor or refusal to accept delivery, as of the date of such
refusal, in the case of personal delivery, or three (3) days after the day so
mailed, or one (1) business day after sent by nationally recognized overnight
courier. Either party may, by notice as aforesaid actually received, designate a
different address or addresses for communications intended for it. Any and all
notices of default which Assignee may give to Landlord or any subtenant under
the Subleases shall simultaneously be given to Assignor. Copies of any and all
notices of default which Assignee may receive from Landlord or any subtenant
under the Subleases shall immediately be delivered to Assignor.

     5. Broker. Each party hereto covenants, warrants and represents to the
other party that it has had no dealings, conversations or negotiations with any
broker concerning the execution and delivery of this Assignment except as may
otherwise be specified in the Purchase Agreement. Each party hereto agrees to
defend, indemnify and hold harmless the other party against and from any claims
for any brokerage commissions and all costs, expenses and liabilities in
connection therewith, including, without limitation, reasonable attorneys' fees
and disbursements, arising out of its respective representations and warranties
contained in this Section being untrue. The provisions of this Section shall
survive the expiration or earlier termination of this Assignment.

     6. Costs of Assignment. All taxes and other governmental charges and fees,
if any, including, without limitation, any and all transfer taxes, stamp taxes,
sales tax and recording fees, relating to this Assignment shall be paid by the
party against whom such taxes, charges, and fees are assessed.

     7. Indemnification. Assignor and Assignee hereby reaffirm the
indemnification obligations set forth in the Purchase Agreement.

     8. Consent of Landlord. This Assignment is specifically conditioned upon
Assignor obtaining the consent of Landlord to this assignment.

     9. Successors and Assigns: Further Actions. This Assignment shall be
binding upon all successors and assigns of the parties hereto. The parties
hereto shall execute and
<PAGE>

deliver such further and additional instruments, agreements and other documents
which may be necessary to evidence or carry out the provisions of this
Assignment.

     10. Entire Agreement. This Assignment supersedes all agreements previously
made between the parties hereto relating to the subject matter contained herein.

     11. No Waiver. No delay or failure by any party hereto to exercise any
rights under this Assignment, and no partial or single exercise of that right,
shall constitute a waiver of that or any other right, unless otherwise expressly
provided herein.

     12. Applicable Law. This Assignment shall be construed in accordance with
and governed by the laws of the State of New York.

     13. Counterparts. This Assignment may be executed in two counterparts, each
of which shall be deemed an original, but both of which together shall
constitute one and the same instrument.

     WITNESS WHEREOF, the parties hereto have executed this Assignment on the
date first above written.

                                           ASSIGNOR:
                                           ZD INC.

                                           By:    /s/ J. MALCOLM MORRIS
                                                  ------------------------------
                                           Name:  J. Malcolm Morris
                                                  ------------------------------
                                           Title: Sr. V.P.
                                                  ------------------------------

                                           ASSIGNEE:
                                           ZIFF DAVIS PUBLISHING INC.

                                           By:    /s/ DANIEL H. BLUMENTHAL
                                                  ------------------------------
                                           Name:  Daniel H. Blumenthal
                                                  ------------------------------
                                                  President
                                                  ------------------------------
<PAGE>

State of New York, )
                   ) ss.:
County of New York )

     On the 4th day of April, in the year 2000 before me the undersigned
personally appeared J. Malcolm Morris, personally know to me or proved to me on
the basis of satisfactory evidence to be the individual whose name is subscribed
to the within instrument and acknowledged to me that he/she executed the same in
his/her capacity as Senior V.P. of ZD Inc., and that by his/her signature on the
instrument, the individual, or the person upon behalf of which the individual
acted, executed the instrument.

/s/ Eugene Hom                                          EUGENE HOM
--------------------------------------        NOTARY PUBLIC, State of New York
Signature and Office of individual                     No. 41-4929038
taking acknowledgment                            Qualified in Queens County
                                            Certificate filed in New York County
                                              Commission Expires June 25, 2000

State of Illinois )
                  ) ss.:
County of Cook    )

     On the 5th day of April, in the year 2000 before me the undersigned
personally appeared Daniel H. Blumenthal, personally know to me or proved to me
on the basis of satisfactory evidence to be the individual whose name is
subscribed to the within instrument and acknowledged to me that he/she executed
the same in his/her capacity as President of Ziff Davis Publishing Inc. and that
by his/her signature on the instrument, the individual, or the person upon
behalf of which the individual acted, executed the instrument.

/s/ Cynthia M. Wasik                                       [Seal]
----------------------------------------     ----------------------------------
Signature and Office of individual
taking acknowledgment                                 Cynthia M. Wasik
                                              Notary Public, State of Illinois
                                             My Commission Expires May 12, 2002
                                             ----------------------------------

<PAGE>

                                   Schedule 1

All that certain plot, piece or parcel of land situate, lying and being in the
Borough of Manhattan, City, County and State of New York, bounded and described
as follows:

BEGINNING at the intersection of the northerly side of East 27th Street with the
easterly side of Madison Avenue;

THENCE along said side of Madison Avenue in a northerly direction, 197 feet 6
inches to the southerly side of East 28th Street;

THENCE along said side of East 28th Street, a distance of 275 feet to a point
which is distant 150 feet westerly as measured along said side of East 28th
Street from the Westerly side of Park Avenue South;

THENCE southerly and parallel with said side of Park Avenue South 197 feet 6
inches to the northerly side of East 27th Street; and

THENCE westerly along said side of East 27th Street, a distance of 275 feet to
the point of place of BEGINNING.

TOGETHER WITH the benefits and subject to the burdens of an Agreement dated
November 20, 1995 between New York Life Insurance Company and 63 Madison
Associates, L.P. and recorded in the Office of the New York City Register's
Office on January 10, 1996 in Reel 2280 page 174.<PAGE>

                                                                   EXHIBIT 10.27

                             AGREEMENT OF SUBLEASE

                                    between

                              ZD Inc., Sublandlord

                                      and

                           Ziff-Davis Inc., Subtenant

                              Subleased Premises:
                              ------------------

                             The Entire 10th Floor
                               63 Madison Avenue
                           New York, New York  10016
<PAGE>

                               TABLE OF CONTENTS

1.   Subleasing of Subleased Premises............................   1
2.   Term........................................................   1
3.   Fixed Rent and Additional Rent..............................   1
4.   Subordination to and Incorporation of the Lease.............   3
5.   Use.........................................................   4
6.   Covenants with Respect to the Lease.........................   4
7.   Services and Repairs........................................   4
8.   Early Termination Rights....................................   5
9.   Consents....................................................   5
10.  Termination of Lease........................................   5
11.  Sublease, Not Assignment....................................   6
12.  Damage, Destruction, Fire and Other Casualty; Condemnation..   6
13.  No Waivers..................................................   6
14.  Notices.....................................................   6
15.  Broker......................................................   6
16.  Condition of the Subleased Premises.........................   6
17.  Additional Rights of Sublandlord/Subtenant..................   7
18.  Assignment, Subletting......................................  11
19.  Memorandum of Sublease......................................  11
20.  Nondisturbance..............................................  11
21.  Miscellaneous...............................................  11
22.  Related Corporation.........................................  12

                                       i
<PAGE>

EXHIBIT A - FIXED RENT

EXHIBIT B - SUBLANDLORD'S SUBCELLAR 1 LEVEL INCOMING SERVICE ROOM

EXHIBIT C - SUBCELLAR 1 TELECOMMUNICATIONS RISER CONDUIT DIAGRAM

EXHIBIT D - LOCATION OF PORTION OF ROOF DEDICATED FOR
              SUBTENANT'S USE

EXHIBIT E - MEMORANDUM OF SUBLEASE

SCHEDULE 1 - UTILIZATION OF SYSTEMS AND SERVICES

                                       ii
<PAGE>

     AGREEMENT OF SUBLEASE (this "Sublease"), made this 10th day of March, 2000,
between ZD Inc., a Delaware corporation, having an office at 63 Madison Avenue,
New York, New York 10016 ("Sublandlord"), and Ziff-Davis Inc., a Delaware
corporation, having an office at 63 Madison Avenue, New York, New York 10016
("Subtenant").

                              W I T N E S S E T H:
                              - - - - - - - - - -

     WHEREAS, by that certain lease dated as of January 15, 1998, between 63
Madison Associates, L.P. ("Landlord"), as landlord, and Ziff-Davis Inc. n/k/a ZD
Inc., as tenant, as amended by that certain letter agreement dated September 23,
1999 between Landlord and Sublandlord (as so amended, the "Lease"), Landlord is
leasing to Sublandlord Concourse Level "B-2" and the entire 8th, 9th, 10th,
11th, 12th, 13th, 14th, and 15th floors (collectively, the "Leased Premises") of
the building (the "Building") known as 63 Madison Avenue, New York, New York
10016 as more particularly described in the Lease; and

     WHEREAS, Sublandlord desires to sublease to Subtenant the entire 10th floor
of the Building (the "Subleased Premises") and Subtenant desires to hire the
Subleased Premises from Sublandlord on the terms and conditions contained
herein.

     NOW, THEREFORE, in consideration of the mutual covenants herein contained,
it is mutually agreed as follows:

     1. Subleasing of Subleased Premises. Sublandlord hereby subleases to
        --------------------------------
Subtenant, and Subtenant hereby hires from Sublandlord, the Subleased Premises,
upon and subject to the terms and conditions hereinafter set forth.

     2. Term. The term (the "Term") of this Sublease shall commence on April 1,
        ----
2000 (the "Commencement Date") and shall terminate on the Expiration Date of the
Lease (the "Sublease Expiration Date"), or on such earlier date upon which the
Term shall expire or be cancelled or terminated pursuant to any of the
conditions or covenants of this Sublease or pursuant to law.  Promptly after the
determination of the Expiration Date of the Lease, Sublandlord shall notify
Subtenant thereof.

     3. Fixed Rent and Additional Rent.
        ------------------------------

     3.1 Subtenant shall pay to Sublandlord, commencing on the Commencement Date
and thereafter on the first (1st) day of each month during the Term, Fixed Rent
as set forth on Exhibit A annexed hereto and incorporated herein by reference.
If the Commencement Date shall occur on a date other than the first day of any
calendar month, the Fixed Rent payable hereunder for such month shall be
prorated on a per-diem basis. Promptly after the determination of the dates
comprising Rent Period 1, Rent Period 2, Rent Period 3 and Rent Period 4 under
the Lease, Sublandlord shall notify Subtenant thereof.

     3.2 In addition to the Fixed Rent herein reserved, Subtenant agrees to pay
to Sublandlord, as additional rent, Subtenant's Share (as hereinafter defined)
of the amounts payable by Sublandlord pursuant to Articles 36 and 37 of the
Lease on account of increases in Real Estate Taxes and increases in Operating
Expenses. Operating Expenses and Real Estate
<PAGE>

Taxes shall be payable by Subtenant to Sublandlord in the same manner as
corresponding payments are payable by Sublandlord to Landlord under the Lease.
The term "Subtenant's Share" shall mean a fraction, the numerator of which shall
be the number of rentable square feet in the Subleased Premises, and the
denominator of which shall be the total number of rentable square feet in the
Leased Premises. As of the date hereof, the Subleased Premises contain 49,140
rentable square feet, the Leased Premises contain 399,773 rentable square feet
and Subtenant's Share is 12.29%. In the event there is an increase or decrease
in the number of rentable square feet in the Subleased Premises or in the number
of rentable square feet in the Leased Premises after the Commencement Date,
Subtenant's Share shall be adjusted to reflect the ratio that the number of
rentable square feet in the Subleased Premises bears to the total number of
rentable square in the Leased Premises. Further, Subtenant agrees to pay as
additional rent, the full amount of any other charge, fee, cost, sum or expense
which Sublandlord pays or incurs on or after the Commencement Date (x) for the
provision of, or in connection with, any services or supplies provided to or for
the Subleased Premises (or any part thereof) at the request of Subtenant
(including, but not limited to, the furnishing of electric service and other
utilities and concierge services) and (y) as may be required pursuant to the
terms and provisions of the Lease with respect to the Subleased Premises.

     3.3 All Fixed Rent and additional rent or other costs, charges and sums
payable by Subtenant hereunder (collectively, "Rent") shall constitute rent
under this Sublease, and shall be payable to Sublandlord at its address as set
forth in Section 15 hereof, unless Sublandlord shall otherwise so direct in
writing.

     3.4 Subtenant shall promptly pay the Rent as and when the same shall become
due and payable without set-off, offset or deduction of any kind whatsoever,
except as expressly set forth herein or in the Lease as incorporated herein by
reference, and, in the event of Subtenant's failure to pay the same when due
(subject to grace periods provided herein), Sublandlord shall have all of the
rights and remedies provided for herein or at law or in equity, in the case of
non-payment of rent.

     3.5 Subtenant shall have no obligation to pay amounts that have not been
billed to Subtenant hereunder within ninety (90) days after such sums are billed
by Landlord to Sublandlord in a timely manner as required pursuant to the Lease.
Further, in the event Sublandlord shall defer payments due by it under the Lease
in accordance with the provisions of the Lease, Subtenant shall have the right
to similarly defer corresponding payments due by it hereunder until the date
Sublandlord 's deferred payments under the Lease are due and payable.
Subtenant's liability for Rent due under this Sublease accruing during the Term,
and Sublandlord's obligation to refund overpayments of or adjustments to Rent
paid to it by Subtenant, shall survive the expiration or sooner termination of
this Sublease.

     3.6 Sublandlord shall promptly furnish to Subtenant a copy of each notice
or statement from Landlord affecting the Subleased Premises. If Sublandlord
disputes the correctness of any such notice or statement and if such dispute is
resolved in Sublandlord's favor, or if Sublandlord shall receive any refund of
additional rent without a dispute, Sublandlord shall promptly pay to Subtenant
any refund (after deducting from the amount of any such refund all expenses,
including court costs and reasonable attorneys' fees, incurred by Sublandlord in
resolving any such dispute) received by Sublandlord in respect (but only to the
extent) of any

                                       2
<PAGE>

related payments of additional rent made by Subtenant less any amounts
theretofore received by Subtenant directly from Landlord and relating to such
refund.

     3.7 Subtenant shall pay any commercial rent or occupancy tax with regard to
the Subleased Premises either to the taxing authority, or, if appropriate, to
Sublandlord, as Additional Rent, at least five (5) business days before the due
date of each and every such tax payment to the taxing authority.

     4. Subordination to and Incorporation of the Lease.
        -----------------------------------------------

     4.1 This Sublease is in all respects subject and subordinate to the terms
and conditions of the Lease (a true and complete copy of which has been
furnished by Sublandlord to Subtenant), and to all matters to which the Lease is
subject and subordinate. Sublandlord represents that a true and complete copy of
the Lease has been furnished by Sublandlord to Subtenant.

     4.2 Except as otherwise expressly provided in, or otherwise inconsistent
with, this Sublease, or to the extent not applicable to the Subleased Premises,
the terms, provisions, covenants, stipulations, conditions, rights, obligations,
remedies and agreements contained in the Lease are incorporated in this Sublease
by reference, and are made a part hereof as if herein set forth at length,
Sublandlord being substituted for the "Landlord" under the Lease, Subtenant
being substituted for the "Tenant" under the Lease, and Subleased Premises being
substituted for "demised premises" or "premises" under the Lease, except that
the following provisions of the Lease shall be deemed deleted therefrom and
shall have no force and effect as between Sublandlord and Subtenant: (P) 7(C);
(P) 7(D); (P) 7(E); (P) 11(C); (P) 11(D); (P) 11(E); (P) 19(B); (P) 23; (P)
30(B); (P) 35(A); (P) 35(G); (P) 39; (P) 40; (P) 44; (P) 49(A); (P) 49(B); (P)
49(D); (P) 52; (P) 54; (P) 55; (P) 56; all portions of Exhibit A other than the
portion thereof which delineates the Subleased Premises; Exhibits B, B-1, B-2,
B-3, B-4, B-5, C, E, E-1, K, M, N, O, P-1 and R.

     In addition, certain provisions of the Lease as incorporated herein shall
be modified as set forth elsewhere in this Sublease or as hereinafter provided:

          (1)  With respect all applicable provisions of the Lease pursuant to
               which Tenant shall have an exclusive right to use any portion of
               the Building, Subtenant shall have a non-exclusive right to use
               such portion of the Building in common with Sublandlord and/or
               Sublandlord's assignees and other subtenants.

          (2)  Subtenant shall not be entitled any abatement of Rent pursuant to
               Subparagraph 28(C) of the Lease unless Sublandlord is entitled to
               an abatement with respect to its corresponding obligation under
               the Lease.

          (3)  Sublandlord shall deliver to Subtenant a copy of any Extension
               Notice delivered by Sublandlord to Landlord pursuant to Article
               53 of the Lease simultaneously with Sublandlord's delivery of
               such Extension Notice to Landlord. Anything in Article 53 of the
               Lease as incorporated herein by reference to the contrary

                                       3
<PAGE>

               notwithstanding, (a) Subtenant shall have the right to extend the
               term of this Sublease if and only if Sublandlord extends the term
               of the Lease for a corresponding period, (b) subject to the
               foregoing, Subtenant may exercise such right to extend the Term
               of this Sublease by notice to Sublandlord given within sixty (60)
               days after Subtenant's receipt of a copy of Sublandlord's
               Extension Notice delivered in accordance with the provisions of
               the Lease and (c) in the event of any such extension of the Term
               of this Sublease, the Fixed Rent hereunder during any such
               extension shall be equal to the corresponding fixed rent payable
               under the Lease in respect of the Subleased Premises for such
               Extension Term.

          (4)  Subtenant shall have no obligation to maintain and/or repair any
               portion of the Building other than the Subleased Premises.

     5. Use. Subtenant shall use and occupy the Subleased Premises for the
        ---
permitted use specified in Article 2 of the Lease and for no other purpose.

     6. Covenants with Respect to the Lease.
        -----------------------------------

     6.1 Neither Sublandlord nor Subtenant shall do anything that would
constitute a default under the Lease or omit to do anything that such party is
obligated to do under the terms of this Sublease so as to cause there to be a
default under the Lease.

     6.2 Each party shall promptly deliver to the other party copies of all
notices, requests or demands which relate to the Subleased Premises or the use
or occupancy thereof after receipt of same from Landlord. Without limitation of
the foregoing, Sublandlord shall (i) deliver a copy of any notice of default
sent by Sublandlord under the lease simultaneously with its delivery of such
notice of default to Landlord and (ii) promptly after Sublandlord's receipt of
any notice of default received by Sublandlord under the Lease, deliver a copy of
same to Subtenant.

     7. Services and Repairs. Notwithstanding anything to the contrary contained
        --------------------
in the Lease, Sublandlord shall not be required to provide any of the services
that Landlord has agreed to provide pursuant to the Lease (or required by law),
or furnish the electricity to the Subleased Premises that Landlord has agreed to
furnish pursuant to the Lease (or required by law), or make any of the repairs
or restorations that Landlord has agreed to make pursuant to the Lease (or
required by law), or reimburse Subtenant for any repairs or restoration that
Subtenant may make pursuant to the Lease (as incorporated herein by reference)
or take any other action that Landlord has agreed to provide, furnish, make,
comply with, or take, or cause to be provided, furnished, made, complied with or
taken under the Lease, but at Subtenant's request, Sublandlord agrees to use all
diligent efforts to obtain the same from Landlord (provided, however, that
Sublandlord shall not be obligated to use such efforts or take any action which
might give rise to a default under the Lease), in which event Subtenant shall be
responsible for Subtenant's Share of the cost incurred by Sublandlord to obtain
the same from Landlord, and Subtenant shall rely upon, and look solely to,
Landlord for the provision, furnishing or making thereof or compliance
therewith. If Landlord shall default in the performance of any of its

                                       4
<PAGE>

obligations under the Lease, Sublandlord shall, at Subtenant's request, timely
institute and diligently prosecute any action or proceeding which Subtenant, in
its reasonable judgment, deems meritorious, in order to have Landlord make such
repairs, furnish such electricity, provide such services or comply with any
other obligation of Landlord under the Lease or as required by law, in which
event Subtenant shall be responsible for Subtenant's Share of the cost incurred
by Sublandlord by reason of such action or proceeding. Notwithstanding the
foregoing, Subtenant shall have the right to contact Landlord on a direct basis
in respect of regular maintenance and operational issues.

     8. Early Termination Rights. Subtenant shall have the right to terminate
        ------------------------
this Sublease by notice to Sublandlord given no less than six (6) months prior
to the effective date of such early termination, in which event this Sublease
shall expire as of the date specified in Subtenant's notice and, provided that
Subtenant shall not theretofore have sent a notice to Sublandlord terminating
this Sublease pursuant to this sentence, Sublandlord shall have the right to
terminate this Sublease by notice to Subtenant given no less than twelve (12)
months prior to the effective date of such early termination, in which event
this Sublease shall expire as of the date specified in Sublandlord's notice.
Notwithstanding the foregoing, in no event shall the date of early termination
arising by reason of either party's notice given pursuant to the immediately
preceding sentence occur prior to the tenth (10th) anniversary of the
Commencement Date.

     9. Consents. Sublandlord agrees that whenever its consent or approval is
        --------
required hereunder, or where something must be done to Sublandlord's
satisfaction, it shall not unreasonably withhold or delay such consent or
approval. If Landlord shall withhold its consent or approval in connection with
this Sublease or the Subleased Premises in any instance where, under the Lease,
the consent or approval of Landlord may not be unreasonably withheld, and if
Subtenant shall contend that Landlord has unreasonably withheld such consent, at
Subtenant's election, (i) Sublandlord, upon the request and at the expense of
Subtenant, shall timely institute and diligently prosecute any action or
proceeding which Subtenant, in its reasonable judgment, deems meritorious, in
order to dispute such action by Landlord, or (ii) Subtenant, to the extent
allowable under the Lease, may institute and prosecute such action or proceeding
in the name of Sublandlord, provided that Subtenant shall keep Sublandlord
informed of its actions and shall not take any action which might give rise to a
default under the Lease.

     10. Termination of Lease. In the event of a default under the Lease which
         --------------------
results in the termination of the Lease, Subtenant shall, at the option of
Landlord, attorn to and recognize Landlord as sublandlord hereunder and shall,
promptly upon Landlord's request, execute and deliver all instruments necessary
or appropriate to confirm such attornment and recognition. Notwithstanding such
attornment and recognition, Landlord shall not (a) be liable for any previous
act or omission of the sublandlord under this Sublease which shall not then be
continuing, (b) be subject to any offset, not expressly provided for in this
Sublease, which shall have accrued to Subtenant hereunder against said
sublandlord, or (c) be bound by any modification of this Sublease or by any
prepayment shall have been previously approved in writing by Landlord. Subtenant
hereunder hereby waives all rights under any present or future law to elect, by
reason of the termination of the Lease, to terminate this Sublease or surrender
possession of the Subleased Premises.

                                       5
<PAGE>

     11. Sublease, Not Assignment. Notwithstanding anything contained herein,
         ------------------------
this Sublease shall be deemed to be a sublease of the Subleased Premises and not
an assignment, in whole or in part, of Sublandlord's interest in the Lease.

     12. Damage, Destruction, Fire and Other Casualty; Condemnation.
         ----------------------------------------------------------
Notwithstanding any contrary provision of this Sublease or the provisions of the
Lease herein incorporated by reference, Subtenant shall not be entitled to an
abatement of Rent by reason of a casualty or condemnation affecting the
Subleased Premises unless Sublandlord is entitled to an abatement with respect
to its corresponding obligation under the Lease.

     13. No Waivers. Failure by Sublandlord or Subtenant in any instance to
         ----------
insist upon the strict performance of any one or more of the obligations of the
other party under this Sublease, or to exercise any election herein contained,
shall in no manner be or be deemed to be a waiver by Sublandlord or Subtenant,
as the case may be, of any of such other party's defaults or breaches hereunder
or of any of such other party's rights and remedies by reason of such defaults
or breaches, or a waiver or relinquishment for the future of the requirement of
strict performance of any and all of such other party's obligations hereunder.

     14. Notices. Except as otherwise specifically provided herein, any notice,
         -------
statement, demand, consent, approval, advice or other communication required or
permitted to be given, rendered or made by either party to the other, pursuant
to this Sublease or pursuant to any applicable law or requirement of public
authority (collectively, "communications") shall be in writing and shall be
deemed to have been properly given, rendered or made only if sent by personal
delivery, or registered or certified mail, return receipt requested, posted in a
United States post office station in the continental United States, or by a
nationally recognized overnight courier, in each case addressed (i) to Subtenant
at its address first above written, Attention: President and (ii) to
Sublandlord, at its address first above written, Attention: President. A copy of
each communication to either Sublandlord or Subtenant shall also be sent to
Clifford Chance Rogers & Wells LLP, 200 Park Avenue, New York, New York 10166,
Attention: Joanne Feil, Esq. All such communications shall be deemed to have
been given, rendered or made when delivered on the date such communication is
actually received as evidenced by a written receipt therefor or refusal to
accept delivery, as of the date of such refusal, in the case of personal
delivery, or three (3) days after the day so mailed, or one (1) business day
after sent by nationally recognized overnight courier. Either party may, by
notice as aforesaid actually received, designate a different address or
addresses for communications intended for it.

     15. Broker. Each party hereto covenants, warrants and represents to the
         ------
other party that it has had no dealings, conversations or negotiations with any
broker concerning the execution and delivery of this Sublease. Each party hereto
agrees to defend, indemnify and hold harmless the other party against and from
any claims for any brokerage commissions and all costs, expenses and liabilities
in connection therewith, including, without limitation, reasonable attorneys'
fees and disbursements, arising out of its respective representations and
warranties contained in this Section 15 being untrue. The provisions of this
Section 15 shall survive the expiration or earlier termination of this Sublease.

     16. Condition of the Subleased Premises. Subtenant represents that it has
         -----------------------------------
made or caused to be made a thorough examination of the Subleased Premises and
is familiar

                                       6
<PAGE>

with the condition of every part thereof. Subtenant agrees to accept the
Subleased Premises in its "as is" condition on the date hereof, reasonable wear
and tear between the date hereof and the Commencement Date excepted. Anything in
the Lease as incorporated herein by reference to the contrary notwithstanding,
Sublandlord has not made and does not make any representations or warranties as
to the physical condition of the Subleased Premises, the use to which the
Subleased Premises may be put, or any other matter or thing affecting or
relating to the Subleased Premises, except as specifically set forth in this
Sublease. Sublandlord shall have no obligation whatsoever to alter, improve,
decorate or otherwise prepare the Subleased Premises for Subtenant's occupancy.

     17. Additional Rights of Sublandlord/Subtenant. Anything herein to the
         ------------------------------------------
contrary notwithstanding:

     17.1 Subject to the prior consent of Landlord if and solely to the extent
required pursuant to the Lease, during the entire Term hereof:

          (1)  Subtenant shall have the right to connect to and use
               Sublandlord's generator. Sublandlord shall maintain said
               generator in good operating condition, and Subtenant shall pay
               Subtenant's Share of Sublandlord's generator costs, as determined
               pursuant to paragraph 4 of Schedule 1 attached hereto and by this
               reference made a part hereof. Such charges shall be set forth in
               Sublandlord's monthly invoice to Subtenant for Rent.

          (2)  Subtenant shall have the right to connect to and use
               Sublandlord's chiller. Subtenant may at Subtenant's election and
               Subtenant's sole cost and expense install a separate meter to
               measure the consumption of chilled water utilized within the
               Subleased Premises, provided that prior to the installation of
               such separate meter, Subtenant shall pay Subtenant's Share of
               Sublandlord's costs with respect to the use of chilled water in
               the Leased Premises, which charges shall be set forth in
               Sublandlord's monthly invoice to Subtenant for Rent payable
               hereunder and shall be substantiated with sufficient
               documentation submitted to Subtenant together with such monthly
               invoice. So long as Subtenant uses Sublandlord's chiller,
               Sublandlord shall maintain same in good operating condition.

          (3)  Subtenant shall have the right to connect to and use
               Sublandlord's data and telecommunications cabling and associated
               conduit(s) serving the Subleased Premises as more particularly
               described in paragraph 1 of Schedule 1. Sublandlord shall
               maintain such data and communications cabling and associated
               conduit(s) in good operating condition, provided that Subtenant
               shall have the right to obtain access to such data and
               telecommunications cabling and associated conduit(s) (or, as
               necessary, Sublandlord's data and telecommunications cabling and
               associated conduit serving other

                                       7
<PAGE>

               portions of the Leased Premises) to maintain, upgrade or respond
               to emergencies with respect to the data and telecommunications
               cabling and associated conduit(s) serving the Subleased Premises,
               in an emergency immediately after Subtenant orally advises
               Sublandlord of the need for such access, and otherwise within
               four (4) hours after Subtenant orally advises Sublandlord of the
               need for such access. In the event Sublandlord subleases all or
               any portion of Subcellar 1 Level (referenced in the Lease as
               Concourse Level "B-2") to any entity other than Subtenant and/or
               other portions of the Leased Premises other than the Subleased
               Premises to an entity other than Subtenant, Sublandlord shall
               take all necessary action, at no cost to Subtenant, to protect
               the integrity of Subtenant's data and telecommunications cabling
               and associated conduit(s) located in Subcellar 1 Level.

          (4)  Subtenant shall have the right to connect to (i) incoming service
               conduits and utilize spare conduits and service rooms as more
               particularly described in paragraph 2 of Schedule 1 and (ii)
               Sublandlord's incoming service room located on Subcellar 1 Level
               as shown on Exhibit B annexed hereto (the "Incoming Service
               Room"). Subtenant shall have the right, at its expense, to run
               cables from the Incoming Service Room to achieve access to the
               Subleased Premises as shown on Exhibit C annexed hereto. In the
               event Sublandlord subleases all or any portion of Subcellar 1
               Level to an entity other than Subtenant, Sublandlord shall take
               all necessary action, at no cost to Subtenant, to protect the
               integrity of the Incoming Service Room and Subtenant's cables run
               therefrom or to provide, at no expense to Subtenant, the right to
               connect to alternate incoming service.

          (5)  Subtenant shall have the right to use that portion of the roof of
               the Building shown on Exhibit D annexed hereto to install,
               maintain and use Roof Equipment pursuant to Article 48 of the
               Lease and as more particularly described in paragraph 3 of
               Schedule 1.

          (6)  Subject to Landlord's consent, Subtenant shall have the right (a)
               to install an identification of Subtenant's name in 25% of the
               header portion of Sublandlord's directory software, (b) to
               utilize the electronic directory in the Z-D Lobby, (c) to list in
               such electronic directory all employees, floor numbers and
               departments applicable to the Subleased Premises and/or
               Subtenant's use thereof and such other information as Subtenant
               shall reasonably require, (d) to install a computer disc in such
               electronic directory and (e) to update the information stored in
               such computer disc on a periodic basis as required by Subtenant.

                                       8
<PAGE>

          (7)  Subtenant shall have the right to install an electronic directory
               located in the Z-D Lobby and to otherwise utilize the Z-D Lobby
               and systems located therein to the extent and in the manner set
               forth in paragraph 5 of Schedule 1.

          (8)  Subtenant shall have the right to use Sublandlord's cafe in the
               Building so long as same exists.

          (9)  Subtenant shall have the right to use Sublandlord's convention
               and meeting rooms located on Subcellar 1 Level and shall pay to
               Sublandlord a fee of $100 per hour for the use of such rooms on a
               first come-first serve basis, provided that Sublandlord shall
               have the right to exercise a priority to use any Town Center Room
               on at least two (2) weeks prior written notice to Subtenant or
               any other meeting room on at least forty-eight (48) hours prior
               written notice to Subtenant. Notwithstanding the foregoing,
               Sublandlord shall not have right to exercise any such priority to
               use one Town Center Room per week for a time and location
               specified by Subtenant.

          (10) Subtenant shall have access to and the right to use the 28th
               Street Loading Dock Bays subject to Sublandlord's rights with
               respect thereto pursuant to Article 28 of the Lease.

          (11) Subtenant shall have the right to use the freight elevator and
               the right to obtain access through Subcellar 1 Level from the
               loading dock to the freight elevator. In the event Sublandlord
               subleases all or any portion of Subcellar 1 Level, Sublandlord
               shall maintain an access corridor on Subcellar 1 Level from the
               loading dock to the freight elevator sufficient to allow for
               Subtenant's continued access through Subcellar 1 Level from the
               loading dock to the freight elevator.

          (12) So long as Sublandlord uses the Messenger Center, Subtenant and
               Subtenant's employees and invitees shall have the right to pass
               through same to obtain access from the street to the freight
               elevator or the Z-D Lobby to the Subleased Premises.

          (13) Subtenant shall install a security system for the Subleased
               Premises compatible with Sublandlord's existing security system
               per paragraph 13 of Schedule 1, and Sublandlord agrees that, if
               Sublandlord should replace its existing security system, such
               replacement security system shall maintain compatibility with
               Subtenant's security system.

          (14) During the first year of the Term hereof, Subtenant shall have
               the right to issue security passes in Sublandlord's security
               system.

                                       9
<PAGE>

               Such security passes shall provide access limited to the
               Subleased Premises.

     17.2 During the first year of the Term hereof, Sublandlord shall allow
Subtenant to connect to and use Sublandlord's data and voice equipment, IDF
closet, telecommunications equipment, security system, microlite lighting
control system and all other systems and equipment of Sublandlord presently
serving the Subleased Premises as more particularly described in paragraphs 6
through 13 of Schedule 1. Within the first year of the Term hereof, Subtenant
shall cause the Subleased Premises to operate independently from the balance of
the Leased Premises with respect to all such systems and equipment described in
the immediately preceding sentence, provided, however, that with respect to each
of the foregoing systems and equipment, until Subtenant shall achieve such
independent operation, Subtenant shall pay Subtenant's Share of Sublandlord's
costs with respect thereto, which charges shall be set forth on Sublandlord's
monthly invoice to Subtenant for Rent payable hereunder and shall be
substantiated with sufficient documentation submitted to Subtenant together with
such monthly invoice. Sublandlord shall maintain in good operational condition
all systems and equipment described in this Subsection 17.2 until Subtenant
shall have segregated such systems and equipment from those serving the
Subleased Premises. Notwithstanding the provisions of this Section 17.2,
Subtenant shall have no obligation to cause the Subleased Premises to operate
independently from the balance of the Leased Premises with respect to the
systems and equipment described in Section 17.1 hereof.

     17.3 During the entire Term hereof, Subtenant shall pay Subtenant's Share
of Sublandlord's costs with respect to gas consumed within the Leased Premises,
which charges shall be set forth in Sublandlord's monthly invoice to Subtenant
for rent payable hereunder and shall be substantiated with sufficient
documentation submitted to Subtenant together with such invoice.

     17.4 (1)  Subtenant shall have the right to connect to and use
               Sublandlord's satellite dish for the Leased Premises and all
               cabling and equipment required for its proper operation in the
               manner and to the extent provided in paragraph 3 of Schedule 1.

          (2)  In the event Subtenant shall desire cable television within the
               Subleased Premises, it shall enter into an agreement directly
               with the vendor providing cable television to the Building for
               the provision of same, in the manner and to the extent provided
               in paragraph 8 of Schedule 1.

     17.5 Notwithstanding anything to the contrary contained herein, Sublandlord
may discontinue the provision or maintenance of any service or supplies which it
had been providing or maintaining on a voluntary basis provided that Sublandlord
shall give Subtenant sixty (60) days' written notice (or such lesser period of
notice as is required by any third party vendor unaffiliated with Sublandlord
who is providing or maintaining such service or supplies) prior to discontinuing
the provision or maintenance of such service or supplies.

                                       10
<PAGE>

     18. Assignment, Subletting. This Sublease may not be assigned or the
         ----------------------
Subleased Premises demised hereunder further sublet, in whole or in part,
without the prior written consent of Landlord in accordance with all the
provisions of the Lease including, without limitation, Section K of Article 11
of the Lease.

     19. Memorandum of Sublease. Sublandlord and Subtenant agree not to record
         ----------------------
this Sublease. The parties shall, contemporaneously with the execution of this
Sublease, execute, acknowledge and deliver a short form or memorandum of this
Sublease in recordable form and otherwise in the form annexed hereto as Exhibit
E. Recording, filing and like charges imposed by any governmental agency to
effect such recording shall be paid by Subtenant. Upon the expiration or
termination of this Sublease, Subtenant, at Sublandlord's request, shall
execute, acknowledge and deliver to Sublandlord all necessary instrument(s) in
recordable form evidencing a termination of this Sublease and sufficient to
discharge any memorandum hereof of record, and Subtenant shall pay for all
recording, filing and like charges imposed by any governmental agency to effect
such recording.

     20.  Nondisturbance.
          --------------

     20.1 Landlord, Sublandlord and Subtenant agree to execute and deliver a
Subordination, Non-Disturbance and Attornment Agreement with respect to this
Sublease in the form required pursuant to Subparagraph 11(S) of the Lease.

     20.2 Landlord agrees to use good faith efforts to obtain from the holder of
any mortgage encumbering the Building as of the date hereof a non-disturbance
agreement for the benefit of Subtenant.

     21.  Miscellaneous.
          -------------

     21.1 This Sublease contains the entire agreement between the parties and
all prior negotiations and agreements are merged in this Sublease. Any agreement
hereafter made shall be ineffective to change, modify or discharge this Sublease
in whole or in part unless such agreement is in writing and signed by the
parties hereto. No provision of this Sublease shall be deemed to have been
waived by Sublandlord or Subtenant unless such waiver be in writing and signed
by Sublandlord or Subtenant, as the case may be. The covenants and agreement
contained in this Sublease shall bind and inure to the benefit of Sublandlord
and Subtenant and their respective permitted successors and assigns.

     21.2 In the event that any provision of this Sublease shall be held to be
invalid or unenforceable in any respect, the validity, legality or
enforceability of the remaining provisions of this Sublease shall be unaffected
thereby.

     21.3 The paragraph headings appearing herein are for purpose of convenience
only and are not deemed to be a part of this Sublease.

     21.4 Capitalized terms used herein shall have the same meanings as are
ascribed to them in the Lease, unless otherwise expressly defined herein.

                                       11
<PAGE>

     21.5 This Sublease is offered to Subtenant for signature with the express
understanding and agreement that this Sublease shall not be binding upon
Sublandlord unless and until Sublandlord shall have executed and delivered a
fully executed copy of this Sublease to Subtenant.

     21.6 All insurance policies required to be obtained by Subtenant under this
Sublease or the Lease shall name Landlord and Sublandlord as additional insured
as their interests may appear.

     21.7 This Sublease shall be governed by, and construed in accordance with,
the laws of the State of New York.

     22. Related Corporation. Pursuant to Subparagraph 11(N) of the Lease,
         -------------------
Sublandlord hereby certifies to Landlord, its successors and assigns that, as of
the date hereof, Subtenant s a "related corporation" (as defined in the Lease).

     IN WITNESS WHEREOF, the parties hereto have duly executed this Agreement of
Sublease as of the date and year first above written.

SUBLANDLORD:  ZD Inc.              SUBTENANT:  Ziff-Davis Inc.

    /s/ J.MALCOLM MORRIS               /s/ DANIEL S. ROSENWEIG
By: _________________________      By: __________________________
      J. Malcom Morris                   Daniel S. Rosenweig
Name: _______________________      Name: ________________________
       Senior Vice President              Director
Title: ______________________      Title: _______________________

With respect to Paragraph 20 only:

LANDLORD:  63 Madison Associates, L.P.

By:  Comfort 63 Madison, Inc., a general partner

     By: ______________________________________
     Name: ____________________________________
     Title: ___________________________________

By:  Loeb Partners Realty and Development
       Corp. a general partner

     By: ______________________________________
     Name: ____________________________________
     Title: ___________________________________

                                       12
<PAGE>

                                   EXHIBIT A

                                   FIXED RENT

                                                                       Monthly
     Period                                           Annual Amount    Amount
     ------                                           -------------    ------

     Commencement Date - last day of Rent Period 1    $1,388,205.00  $115,683.75
     Rent Period 2                                    $1,589,679.00  $132,473.25
     Rent Period 3                                    $1,791,153.00  $149,262.75
     Rent Period 4 - Sublease Expiration Date         $1,995,084.00  $166,257.00
<PAGE>

                                   EXHIBIT B

                        SUBLANDLORD'S SUBCELLAR 1 LEVEL
                             INCOMING SERVICE ROOM
<PAGE>

                                   EXHIBIT C

                         SUBCELLAR 1 TELECOMMUNICATIONS
                             RISER CONDUIT DIAGRAM
<PAGE>

                                   EXHIBIT D

                          LOCATION OF PORTION OF ROOF
                         DEDICATED FOR SUBTENANT'S USE
<PAGE>

                                   EXHIBIT E

                             MEMORANDUM OF SUBLEASE

     THIS MEMORANDUM OF SUBLEASE ("Memorandum") is executed the 10th day of
March, 2000, to evidence for recording purposes the execution of a certain
sublease dated as of March 15, 2000 (the "Sublease"), the relevant terms of
which are set forth below:

     1. The Sublandlord is ZD Inc. ("Sublandlord"), a Delaware corporation
having an office at 63 Madison Avenue, New York, New York 10016.

     2. The Subtenant is Ziff-Davis Inc. ("Subtenant"), a Delaware corporation
having an office at 63 Madison Avenue, New York, New York 10016.

     3. The term of the Sublease shall commence on April 1, 2000 and shall
expire on July 16, 2019, subject to Subtenant's options to extend the same for
two (2) consecutive ten (10) year periods pursuant to the terms and conditions
provided in the Sublease.

     4. The subleased premises (the "Subleased Premises") consist of the entire
tenth (10th) floor of the building known as 63 Madison Avenue, New York, New
York (the "Building"), constituting a portion of the premises demised by
Sublandlord pursuant to that certain lease dated as of January 15, 1998 between
63 Madison Associates, L.P., as landlord, and Sublandlord, as tenant. Schedule A
attached hereto and incorporated herein by reference is a legal description of
the land upon which the Building is situated.

     5. In the event of any conflict between the terms hereof and the terms of
the Sublease, the terms of the Sublease shall govern.

     IN WITNESS WHEREOF, the parties have executed this memorandum of Lease on
the respective dates as set forth on the acknowledgments below:

ZD Inc.                                         Ziff-Davis Inc.

By:                                             By:
    ----------------------------                    -------------------------
Name:                                           Name:
      --------------------------                      -----------------------
Title:                                          Title:
       -------------------------                      -----------------------

After recording, this Memorandum
should be returned to:

Clifford Chance Rogers & Wells LLP
200 Park Avenue
New York, New York  10166
Attn:  Joanne Feil, Esq.

                                      E-1
<PAGE>

State of New York,      )
                        )  ss.:
County of ____________  )

     On the ___________ day of ______________________________, in the year
________ before me the undersigned personally appeared
_____________________________________________ , personally know to me or proved
to me on the basis of satisfactory evidence to be the individual whose name is
subscribed to the within instrument and acknowledged to me that he/she executed
the same in his/her capacity as ______________________________ of ZD Inc., and
that by his/her signature on the instrument, the individual, or the person upon
behalf of which the individual acted, executed the instrument.

Signature and Office of individual

taking acknowledgment

State of New York,      )
                        )  ss.:
County of ____________  )

     On the ___________ day of ______________________________, in the year
________ before me the undersigned personally appeared
_____________________________________________ , personally know to me or proved
to me on the basis of satisfactory evidence to be the individual whose name is
subscribed to the within instrument and acknowledged to me that he/she executed
the same in his/her capacity as ______________________________ of Ziff-Davis
Inc., and that by his/her signature on the instrument, the individual, or the
person upon behalf of which the individual acted, executed the instrument.

Signature and Office of individual
taking acknowledgment

                                      E-2
<PAGE>

                                   Schedule A

All that certain plot, piece or parcel of land situate, lying and being in the
Borough of Manhattan, City, County and State of New York, bounded and described
as follows:

BEGINNING at the intersection of the northerly side of East 27th Street with the
easterly side of Madison Avenue;

THENCE along said side of Madison Avenue in a northerly direction, 197 feet 6
inches to the southerly side of East 28th Street;

THENCE along said side of East 28th Street, a distance of 275 feet to a point
which is distant 150 feet westerly as measured along said side of East 28th
Street from the Westerly side of Park Avenue South;

THENCE southerly and parallel with said side of Park Avenue South 197 feet 6
inches to the northerly side of East 27th Street; and

THENCE westerly along said side of East 27th Street, a distance of 275 feet to
the point of place of BEGINNING.

TOGETHER WITH the benefits and subject to the burdens of an Agreement dated
November 20, 1995 between New York Life Insurance Company and 63 Madison
Associates, L.P. and recorded in the Office of the New York City Register's
Office on January 10, 1996 in Reel 2280 page 174.

                                      E-3
<PAGE>

                                   Schedule 1

                      Utilization of Systems and Services
                      -----------------------------------

     1. Low Voltage Risers

          a.   Sleeves within Riser/IDF Closets (B1 thru 15th floors) - Two (2)
               4" empty riser sleeves shall be dedicated; one in each of the
               East and West riser for Subtenant.

          b.   Sub-Concourse horizontal raceways - Subtenant reserves the right
               to intercept the riser conduits designated for its use and extend
               said conduits to one of the following locations:

               i.   West side conduits shall be extended to the Incoming service
                    room

               ii.  East side conduits shall be extended to the IDF closet at
                    the southeast corner of the sub-concourse.

     2. Incoming Service

          a.   Incoming Service Conduits - One (1) 4" empty conduit in either
               the Northwest or Southwest incoming service point shall be made
               available at the entrance point for Subtenant in the event it
               deems the utilization of same necessary.

          b.   Incoming Service Room - The incoming service room shall be a
               shared room for Sublandlord, Subtenant and any other subtenants
               of Sublandlord. It shall be available to Subtenant 24 hours a
               day/365 days a year. It shall be one of the entrance points for
               any incoming service vendors as Subtenant shall deem necessary.

          c.   Alternate incoming service room - The IDF closet in the southeast
               corner of the sub-concourse (or other mutually agreed upon
               location shall be made available as an alternate incoming service
               room for use by Subtenant should it deem it necessary. It shall
               be available to Subtenant 24 hours a day/365 days a year. It
               shall be one of the entrance points for any incoming service
               vendors as Subtenant shall deem necessary.

          d.   Alternate Incoming service - Subtenant reserves the right to
               access one or the other incoming service points (Northwest and
               Southeast) that are not fed into the incoming service room for
               the purpose of having redundant and diverse services delivered to
               the Subleased Premises. Sublandlord shall cooperate in allowing
               access by Subtenant (or its designated vendor) to the incoming
               service points and extending of services across the sub-concourse
               to the alternate riser location for delivery to the Sublease
               Premises.

                                      S1-1
<PAGE>

          e.   Incoming service cabling - Subtenant reserves the right to
               utilize the spare conduits made available by Sublandlord for
               running new incoming service risers to the Subleased Premises.

     3. Roof System

          a.   Dish Array - Subtenant shall have space reserved on the dish
               array for mounting two (2) dedicated dishes on the dish array for
               Subtenant's exclusive use. Where necessary, Sublandlord shall
               allow access by Subtenant to route cabling through Sublandlord's
               IDF closets and through Sublandlord's existing conduits from the
               15th Floor IDF to the roof and from the 15th Floor IDF to the
               10th Floor IDF for the purposes of providing services to the
               Subleased Premises.

          b.   Spare Satellite Dish Cabling to the Subleased Premises - Three
               (3) spare satellite dish cables installed from the 15th floor IDF
               to the 10th floor IDF for future dish installations shall become
               the property of Subtenant.

     4. Emergency Generator/UPS

          a.   Allocation of Expenses - Subtenant shall be charged its
               proportionate share of the overall costs of operation,
               maintenance, service, etc. with regard to the emergency generator
               and UPS systems. The allocation of expenses associated with the
               emergency generator and the UPS shall be in accordance with one
               of the following methods as selected by Subtenant.

               i.   The basis for determination of proportionate share shall be
                    based upon a rentable square foot of space basis as outlined
                    in the Sublease. This proportionate share allocation also
                    assures Subtenant of the same proportionate share of the
                    overall emergency generator and UPS system capacity (as
                    applied to each system separately).

               ii.  Subtenant shall pay for usage of the emergency generator and
                    UPS systems based upon its actual demand or consumption. The
                    amount established shall be as negotiated between
                    Sublandlord and Subtenant. This shall be determined by
                    placing sub-meter(s) on Subtenant's associated emergency/UPS
                    panels, loads, etc. The costs for the addition of the
                    sub-meters shall be at the sole cost and expense of
                    Subtenant.

     5. Z-D Lobby Technology Systems

          a.   [Intentionally Deleted].

          b.   Special Events - Subtenant reserves the right to use the Z-D
               Lobby area for the purposes of special events or as a
               pre-function area for special events held elsewhere upon written
               notice to Sublandlord and in no event more than four (4)

                                      S1-2
<PAGE>

               times in any twelve (12) month period. During such events, all
               audiovisual systems and sub-systems located in the Z-D Lobby
               shall be made available for Subtenant's use. Subtenant, at its
               sole cost and expense, shall comply with all applicable laws in
               connection with its use of the Z-D Lobby for such events,
               including, without limitation, obtaining all necessary permits
               therefor and shall be responsible for all required clean-up to
               restore the Z-D Lobby to its normal condition.

     6. Voice Systems

          a.   Voice cable risers (twisted pair copper cabling)- Subtenant
               reserves the right to make use of the existing voice risers that
               connect the Subleased Premises to the data center. If so desired,
               it may re-route/extend voice riser cables from the data center on
               the sub-concourse level to alternate locations within the
               sub-concourse level. Cabling that runs up the west riser shall be
               extended to the incoming service room. Cabling that runs up the
               east riser shall be extended to another mutually acceptable
               location within the sub- concourse. The re-routing/extending of
               the existing voice cables can be done outside of the spare
               conduit capacity made available by Sublandlord per Schedule 1,
               paragraph 1. Where necessary, Sublandlord shall allow access by
               Subtenant to route cabling through Sublandlord's IDF closets for
               the purposes of providing services to the Subleased Premises. All
               work performed by Subtenant shall insure that Sublandlord's
               remaining cabling systems and services are not compromised or
               placed at risk.

          b.   Data Center PBX - Within the first year of the Term of the
               Sublease, Subtenant shall remove its telephone cards from the
               current PBX system in the data center, proportionate to the
               number of telephone lines serving the Subleased Premises in
               relation to the total number of telephone lines serving the
               Leased Premises. All of the phone devices located in the
               Subleased Premises shall be the property of Subtenant to utilize
               as it sees fit.

          c.   Horizontal Cabling - All of the horizontal cabling, connectors,
               patch panels, cross connects, etc. located in the Subleased
               Premises to support the voice systems shall be the property of
               Subtenant.

     7. Data Systems

          a.   Data cable risers (fiber optic cabling) - Subtenant reserves the
               right to make use of the existing data risers that connect the
               Subleased Premises to the data center. If so desired, Subtenant
               may re-route/extend data riser cables from the data center on the
               sub-concourse level to alternate locations within the
               sub-concourse level. Cabling that runs up the west riser shall be
               extended to the incoming service room. Cabling that runs up the
               east riser shall be extended to another mutually acceptable
               location within the sub-concourse. The re-routing/extending of
               the existing data cables can be done outside of the spare conduit
               capacity made

                                      S1-3
<PAGE>

               available by Sublandlord. Where necessary, Sublandlord shall
               allow access by Subtenant to route cabling through Sublandlord's
               IDF closets for the purposes of providing services to the
               Subleased Premises. All work performed by Subtenant shall insure
               that Sublandlord's remaining cabling systems and services are not
               compromised or placed at risk.

          b.   IDF closet electronics - All of the data/LAN electronics that are
               located in the IDF closet for the purposes of delivering LAN
               connectivity to the Subleased Premises shall become the property
               of Subtenant. All software, catalogs, warrantees, etc. shall also
               become the property of Subtenant.

          c.   Horizontal Cabling - All of the horizontal cabling, connectors,
               patch panels, patch cords, etc. on the Subleased Premises to
               support the data systems shall be the property of Subtenant.

     8. CATV System

          a.   CATV riser cabling - Within the first year of the Term of the
               Sublease, Subtenant shall cease utilizing Sublandlord's CATV
               riser system. Where appropriate the riser shall be spliced to
               by-pass the Subleased Premises and provide connectivity for the
               balance of the Leased Premises. All of the distribution passive
               components and electronics located within the IDF closet for the
               purposes of serving the horizontal distribution shall remain the
               property of Subtenant. Any rebalancing of the remaining CATV
               system required by Sublandlord to ensure proper operation shall
               be at Sublandlord's expense.

          b.   Horizontal Cabling - All of the horizontal CATV cabling and
               devices located in the Subleased Premises shall remain the
               property of Subtenant.

          c.   New CATV Service - Subtenant reserves the right to bring in new
               CATV service to support the Subleased Premises. The riser cables
               necessary to support this new service shall be run in the
               existing CATV riser sleeve that currently provides CATV service
               to the occupied portion of the Leased Premises. The work will be
               done outside of the spare conduit capacity made available by
               Sublandlord per Schedule 1, paragraph 1. Where necessary,
               Sublandlord shall allow access by Subtenant to route cabling
               through Sublandlord's IDF closets for the purposes of providing
               services to the Subleased Premises. All work performed by the
               sub- tenants shall insure that Sublandlord's remaining cabling
               systems and services are not compromised or placed at risk.

     9. IDF Closets

          a.   IDF Closets - The IDF closets on the Subleased Premises shall
               become the exclusive property of Subtenant. Any access to the
               closet by Sublandlord or its designated vendor shall only be upon
               prior approval of, and shall be supervised

                                      S1-4
<PAGE>

               by, Subtenant. Any expenses incurred by Subtenant for after-hours
               supervision shall paid by Sublandlord. All work performed in the
               IDF closets shall be at a time that is reasonably approved by
               Subtenant.

          b.   Low Voltage Systems Components - All of the patch panels, racks
               frames, electronics, etc. to support the voice, data, CATV,
               security system, etc. shall become the property of Subtenant.

     10. Lighting Control System

          a.   Lighting Control System relay Panels - The relay panels for the
               lighting control system shall be removed from the overall system
               and shall be isolated for Subtenant's exclusive use. Subtenant
               shall provide its own lighting control system control unit to
               make its system operational. Sublandlord shall provide the
               necessary connectivity once Subtenant's panels have been removed
               to ensure proper operation of Sublandlord's overall lighting
               control system.

     11. Building Management System

          a.   Remote Monitoring Interface - Subtenant, at its sole cost and
               expense, shall have the right to install a remote monitoring
               interface to Sublandlord's building management system and place
               it in the Subleased Premises as designated by Subtenant.
               Subtenant shall have the ability to monitor all control points
               and functions that affect the Subleased Premises, but shall not
               have the ability to control those points unless deemed acceptable
               by Sublandlord. Any BMS or control related issues presented to
               Sublandlord by Subtenant shall be addressed in a proactive manner
               and shall be brought to resolution as quickly as possible.

     12. Telephone Numbers

          a.   Subtenant reserves the right to be allocated its proportionate
               share of the DID numbers that currently support Sublandlord and
               Subtenant as a whole. The bank of DID phone numbers allocated to
               Subtenant shall be those that are closest to the numbers that
               currently serve it today.

     13. Security System

          a.   Subtenant Security System - Subtenant shall take ownership of all
               security systems devices located on the Subleased Premises for
               the purposes of isolating and securing Subtenant's perimeter and
               interior. This includes but is not limited to access control
               panels, card readers, door contacts, electric strikes, security
               system panels, CCTV cameras, panic buttons, etc. Subtenant shall
               provide its own security system that will interface with the
               existing security system panels located in Subtenant's IDF
               closets. If any portion of Sublandlord's security system is
               disconnected specifically due to Subtenant's removal of its
               panels from

                                      S1-5
<PAGE>

               Sublandlord's security system, Subtenant shall reconnect such
               disconnected security system components of Sublandlord at
               Subtenant's expense.

          b.   Common Security Components - Common security components such as
               the lobby turnstiles, elevator access, floor access, etc. shall
               remain on Sublandlord's security system. For the purposes of
               control of these components to the extent that they affect
               Subtenant only, a remote administrative terminal shall be
               provided to Subtenant. Sublandlord's security system shall be
               partitioned to allow the administration of access rights by
               Subtenant for its floor and common shared areas. Subtenant, at
               its sole cost and expense, shall install administrative terminals
               and system partitioning. Subtenant shall be responsible for
               maintaining the cardholder's database on both Subtenant's and
               Sublandlord's security systems.

                                      S1-6

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