Document:

<PAGE>
                                                                    EXHIBIT 10.6

                            FIRST AMENDMENT TO LEASE

      THIS FIRST AMENDMENT TO LEASE (the "First Amendment") is made and entered
into this 30 day of December, 1999 by and between PINE STREET INVESTORS I,
L.L.C., a Delaware limited liability company ("Landlord") and ART TECHNOLOGY
GROUP, INC., a Delaware corporation ("Tenant").

                                    RECITALS

A. Landlord and Tenant have previously entered into that certain written Office
Lease, dated October 6, 1999 ( the "Lease"), pursuant to which Landlord leased
to Tenant, and Tenant hired from Landlord, those certain premises comprising
12,931 square feet of rentable area on the 21st floor (the "Premises") in the
office building located at 100 Pine Street Center, San Francisco, California
(the "Building"). Concurrently with the execution of the Lease, Landlord and
Tenant executed a Work Agreement setting forth the terms and conditions under
which initial tenant improvements would be made to the Premises (the "Work
Agreement").

B. Tenant's proposed Plans under the Work Agreement include non-building
standard ceiling lighting fixtures. As a condition to Landlord's approval of
said Plans, Tenant has agreed to pay for the cost of restoring the Premises to a
building standard condition in accordance with the terms and conditions set
forth herein.

C. The parties desire to amend the Lease upon the terms and conditions set forth
herein.

      NOW, THEREFORE, in consideration of the foregoing, Landlord and Tenant
hereby agree as follows:

      1. All capitalized terms not defined herein shall have the meanings
ascribed to them in the Lease or the Work Agreement, as applicable.

      2. The parties acknowledge and agree that Landlord has agreed to the
installation of non-Building standard lighting fixtures in connection with the
Work performed under the Work Agreement, upon the condition that Tenant pay
Landlord for the cost of the restoration of the Premises ceiling to a
Building-standard condition. Notwithstanding anything to the contrary in the
Lease or the Work Agreement (including, without limitation, Article 22 of the
Lease), Tenant hereby agrees to pay for the cost of: (i) removing the ceiling
light fixtures installed as part of the

                                       1
<PAGE>
initial improvements to the Premises under the Work Agreement and (ii) restoring
the Premises ceiling lights and ceiling grid (including tiles) to a building
standard condition (the "Ceiling Restoration"). The parties hereby agree that
the cost of the Ceiling Restoration is equal to $44,218.00 (the "Ceiling
Restoration Cost"). The Ceiling Restoration Cost shall be paid by Tenant by
means of a Letter of Credit (defined below) upon which Landlord will have the
right to draw upon the expiration or earlier termination of the Lease.

      3. Tenant shall deliver and cause to be in effect upon the execution of
this First Amendment, during the Lease Term, and for a period sixty (60) days
after the Expiration Date, an unconditional, irrevocable letter of credit in the
amount of $44,218.00 in favor of Landlord ("Letter of Credit"). The Letter of
Credit shall serve as a means of payment for the Ceiling Restoration Costs. In
accordance with the terms hereof, Tenant shall deliver the Letter of Credit to
Landlord upon the execution of this First Amendment. The Letter of Credit shall
be in a form reasonably acceptable to Landlord and issued by a bank selected by
Tenant and reasonably acceptable to Landlord. Without limiting the generality of
the foregoing, any bank issuing the Letter of Credit shall be a bank that
accepts deposits, maintains accounts, has a local San Francisco office that will
negotiate a letter of credit, and the deposits of which are insured by the
Federal Deposit Insurance Corporation. Without limiting the generality of the
foregoing, the Letter of Credit shall provide: (i) that Landlord shall have the
right to draw upon such letter of credit immediately following the expiration or
earlier termination of the Lease, and (ii) that the issuing bank shall deliver
to Landlord at least sixty (60) days prior written notice of the termination or
expiration of any such Letter of Credit. Tenant shall pay all expenses, points,
or fees incurred by Tenant in obtaining and maintaining the Letter of Credit.
Tenant agrees, upon termination of the Lease, that Landlord shall have the right
to draw upon all of the Letter of Credit to compensate Landlord for the Ceiling
Restoration Cost. The failure by Tenant to provide Landlord with the Letter of
Credit or the failure by Tenant to provide a substitute Letter of Credit meeting
all of the criteria set forth herein on or before thirty (30) days prior to the
expiration or termination of any prior Letter of Credit shall constitute a
material breach of the Lease and be deemed a Default thereunder.

      4. Except as amended hereby, the Lease and the Work Agreement remain
unmodified and in full force and effect. Tenant acknowledges that Landlord is
not in default in the performance of any of its obligations under the Lease and
that Tenant has no claims or setoffs of any kind.

                                       2
<PAGE>
      IN WITNESS WHEREOF, Landlord and Tenant have duly executed this First
Amendment as of the date and year first above written.

LANDLORD:

PINE STREET INVESTORS I L.L.C., a
Delaware Limited Liability Company

By:     Danielson Whitehead, Inc.
        a California corporation,
        as agent for Pine Street
        Investors I, L.L.C.

        By:     /s/ Carl F. Danielson
                -----------------------
        Name:   Carl F. Danielson
                -----------------------
        Title:  Chief Executive Officer
                -----------------------

TENANT:

ART TECHNOLOGY GROUP, INC.,
a Delaware corporation

By: /s/ Paul Shorthose
   --------------------------------
Name:
     ------------------------------
Title:
      -----------------------------

                                       3<PAGE>
                                                                    EXHIBIT 10.7

                        SECOND AMENDMENT TO OFFICE LEASE

      THIS SECOND AMENDMENT TO OFFICE LEASE ("Second Amendment") is made and
entered into this 28th day of August, 2000 by and between PINE STREET INVESTORS
I, L.L.C., a Delaware limited liability company ("Landlord"), and ART TECHNOLOGY
GROUP, INC., a Delaware corporation ("Tenant").

                                    RECITALS

      A. On October 6, 1999, Landlord and Tenant entered into that certain
Office Lease under which Landlord leased to Tenant, and Tenant leased from
Landlord, certain premises comprising the 2lst floor of the building (the
"existing Premises") located at 100 Pine Street, San Francisco, California (the
"Building"). The Office Lease was amended by that certain First Amendment to
Office Lease dated December 30, 1999. The Office Lease and the First Amendment
to Office Lease are referred to collectively herein as the "Lease."

      B. Tenant desires to lease additional office space on the 20th and 25th
floors of the Building to increase its existing Premises and Landlord desires to
lease such space to Tenant on the terms and conditions set forth herein.

      NOW, THEREFORE, in consideration of the mutual promises contained herein
and other good and valuable consideration, the receipt and sufficiency of which
is hereby acknowledged, Landlord and Tenant hereby agree as follows:

                                    AGREEMENT

1. Definitions. Any capitalized terms set forth in this Agreement which are not
expressly defined herein shall have the meanings ascribed to them in the Lease.

2. 25th Floor Space.

      (a) Space. Landlord hereby leases to Tenant and Tenant hereby hires from
Landlord, in addition to the existing Premises, 13,692 rentable square feet of
space comprising the twenty-fifth (25th) floor of the Building (Suite 2500), as
identified on Exhibit A attached hereto and made a part hereof (the "25th Floor
Space").

      (b) Term. The Lease Term for the 25th Floor Space shall commence upon the
earlier of: (i) Tenant's occupancy of such space for purposes of conducting
business therein, (ii) the substantial completion of any initial alterations or
improvements to the 25th Floor Space to be made by Tenant as set forth herein,
or (iii) seventy-five (75) days following Landlord's delivery to Tenant of
possession thereof in shell condition, as more
<PAGE>
particularly described in Exhibit B attached hereto and made a part hereof (the
"25th Floor Commencement Date"). The parties currently anticipate that such
delivery of possession by Landlord shall occur on June 15, 2001 ("25th Floor
Target Delivery Date"). The Lease Term for the 25th Floor Space shall expire on
December 31, 2011, unless sooner terminated as provided in the Lease. If
Landlord, for any reason whatsoever, cannot deliver possession of the 25th Floor
Space to Tenant by the 25th Floor Target Delivery Date, this Second Amendment
and the Lease shall not be void or voidable, the term of the Lease shall not be
extended by such delay, the terms and conditions of the Lease applicable to the
existing Premises and the 2Oth Floor Space (defined below) shall in no way be
affected thereby, and the Landlord shall not be liable to Tenant for any loss or
damage resulting therefrom; provided, however, if Landlord is unable, for any
reason except to the extent caused by Tenant, its contractors, agents or
employees, to deliver possession of the 25th Floor Space to Tenant within one
hundred eighty (180) days from the 25th Floor Target Delivery Date, Tenant
shall, as its sole remedy, have the right to terminate the Lease as to the 25th
Floor Space only by written notice to Landlord any time thereafter until
Landlord delivers the 25th Floor Space to Tenant.

      (c) Base Rent. Tenant shall pay Landlord as Base Rent for the 25th Floor
Space the sum of $95.00 per rentable square foot of the 25th Floor Space per
year, which shall be equal to an annual Base Rent of $1,3OO,74O.OO and a monthly
Base Rent of $108,395.00. Said Base Rent shall be payable commencing as of the
25th Floor Commencement Date, except that Base Rent for the first full calendar
month for which said Base Rent shall be due shall be paid when Landlord delivers
possession of the 25th Floor Space to Tenant as required hereunder. Said Base
Rent shall be in addition to the Base Rent payable for the existing Premises
under Article 3 of the Lease and the 20th Floor Space under the terms and
conditions set forth in Paragraph 3 below. Any Base Rent shall be paid in
advance, on or before the first day of each calendar month during the Lease Term
as set forth in the Lease. If the Commencement Date applicable to the 25th Floor
Space is on a day other than the first day of a calendar month, Base Rent for
the 25th Floor Space shall be prorated for such month.

      (d) Operating Expenses. Tenant shall pay as additional rent Tenant's
Prorata Share attributable to the 25th Floor Space. The parties acknowledge and
agree that Tenant's Prorata Share of Taxes and Operating Expenses attributable
to the 25th Floor Space is 3.402%. The Base Expense Year and Base Tax Year for
calculating Tenant's Prorata Share attributable to the 25th Floor Space is the
calendar year 2001.

      (e) Condition of the 25th Floor Space. Tenant acknowledges and agrees
that, notwithstanding anything to the contrary in Article 6 of the Lease or
Paragraph 3 below, it is leasing the 25th Floor Space in an "as is" condition as
of the date of Landlord's delivery to Tenant of possession thereof, and that
Landlord is not responsible for making any repairs or improvements thereto
except that Landlord agrees to provide the 25th Floor Allowance as set forth in
Paragraph 2(f) below, to delivery the space as expressly set forth in Exhibit B
hereto and Landlord agrees to be responsible for: (i) compliance with the
Americans With Disabilities Act requirements in the Building common areas and
the 25th floor bathrooms to the extent applicable as of the 25th Floor
Commencement Date

                                       2
<PAGE>
and (ii) the corridor wall surrounding the Building core on the 25th floor of
the Building, installed with properly rated sheet rock, taped and ready to
received paint or other Tenant finish (collectively, "Landlord's Work"). The
parties acknowledge and agree that Landlord's Work may take place following
Landlord's delivery of the 25th Floor Space and concurrently with the
construction of initial alterations and improvements to the 25th Floor Space to
be made by Tenant. Tenant further acknowledges and agrees that neither Landlord
nor any agent of Landlord has made any representation or warranty with respect
to the 25th Floor Space, the existing Premises, the Building, the Building
Systems and Equipment or Tenant's business.

      (f) 25th Floor Allowance. Landlord shall provide to Tenant an improvement
allowance in an amount equal to Four Hundred Ten Thousand Seven Hundred Sixty
Dollars ($410,760.00) ("25th Floor Allowance"), to reimburse Tenant for actual
costs incurred by it in connection with the refurbishment, repair, improvement
and/or alteration of the 25th Floor Space. Any repairs, refurbishment,
improvements or alterations shall be completed by Tenant at its own expense, and
subject to the provisions of Article 10 of the Lease. The 25th Floor Allowance,
or any portion thereof, shall be payable by Landlord as the work progresses
within thirty (30) days following receipt of Tenant's disbursement requests
against such allowance as set forth herein. Such requests shall include the
following items, to the extent applicable to the items for which the 25th Floor
Allowance disbursement is being requested: (i) proper receipts for said repairs,
refurbishment, improvements or alterations, or any portions thereof, (ii) a
certification from the contractor performing said work that the sums billed
reflect work actually performed, (iii) executed conditional mechanic's and
materialman's lien releases, in the statutory form, from all parties being paid
from such disbursement, (iv) such other information or documentation as Landlord
may reasonably request.

3. 2Oth Floor Space.

      (a) Space. Landlord hereby leases to Tenant and Tenant hereby hires from
Landlord, in addition to the existing Premises and the 25th Floor Space, 9,947
rentable square feet of space comprising a portion of the twentieth (20th) floor
of the Building (Suite 2000), as identified on Exhibit C attached hereto and
made a part hereof (the "20th Floor Space").

      (b) Term. The Lease Term for the 20th Floor Space shall commence upon the
earlier of: (i) Tenant's occupancy of such space for purposes of conducting
business therein, (ii) the substantial completion of any initial alterations or
improvements to the 20th Floor Space to be made by Tenant as set forth herein,
or (iii) seventy-five (75) days following Landlord's delivery to Tenant of
possession thereof (the "20th Floor Commencement Date"). The parties currently
anticipate that such delivery of possession by Landlord shall occur on April 1,
2001 ("2Oth Floor Target Delivery Date"), The Lease Term for the 20th Floor
Space shall expire on December 31, 2011, unless sooner terminated as provided in
the Lease. If Landlord, for any reason whatsoever, cannot deliver possession of
the 2Oth Floor Space to Tenant by the 20th Floor Target Delivery Date, this
Second Amendment and the Lease shall not be void or voidable, the term of the
Lease shall not be extended by such delay, the terms and conditions of the Lease

                                       3
<PAGE>
applicable to the existing Premises and the 25th Floor Space shall in no way be
affected thereby, and the Landlord shall not be liable to Tenant for any loss or
damage resulting therefrom; provided, however, if Landlord is unable, for any
reason except to the extent caused by Tenant, its contractors, agents or
employees, to deliver possession of the 20th Floor Space to Tenant within one
hundred eighty (180) days from the 20th Floor Target Delivery Date, Tenant
shall, as its sole remedy, have the right to terminate the Lease as to the 20th
Floor Space only by written notice to Landlord any time thereafter until
Landlord delivers the 20th Floor Space to Tenant.

      (c) Base Rent. Tenant shall pay Landlord as Base Rent for the 20th Floor
Space the sum of $92.OO per rentable square foot of the 2Oth Floor Space per
year, which shall be equal to an annual Base Rent of $915,124.OO and a monthly
Base Rent of $76,260.33. Said Base Rent shall be payable commencing as of the
20th Floor Commencement Date, except that Base Rent for the first full calendar
month for which said Base Rent shall be due shall be paid when Landlord delivers
possession of the 20th Floor Space to Tenant. Said Base Rent shall be in
addition to the Base Rent payable for the existing Premises under Article 3 of
the Lease and the 25th Floor Space as set forth herein, Any Base Rent shall be
paid in advance, on or before the first day of each calendar month during the
Lease Term as set forth in the Lease. If the Commencement Date applicable to the
20th Floor Space is on a day other than the first day of a calendar month, Base
Rent for the 20th Floor Space shall be prorated for such month.

      (d) Operating Expenses. Tenant shall pay as additional rent Tenant's
Prorata Share attributable to the 20th Floor Space. The parties acknowledge and
agree that Tenant's Prorata Share of Taxes and Operating Expenses attributable
to the 20th Floor Space is 2.471%. The Base Expense Year and Base Tax Year for
calculating Tenant's Prorata Share attributable to the 20th Floor Space is the
calendar year 2001.

      (e) Condition of 20th Floor Space. Tenant acknowledges and agrees that,
notwithstanding anything to the contrary in Article 6 of the Lease or Paragraph
2 above, it is leasing the 20th Floor Space in its present and "as is"
condition, and that Landlord is not responsible for making any repairs or
improvements thereto except that: (i) Landlord agrees to provide the 20th Floor
Allowance as set forth in Paragraph 2(f) below, and (ii) Landlord agrees to be
responsible for compliance with the American With Disabilities Act requirements
in the Building common areas and the 20th floor bathrooms to the extent
applicable as of the 20th Floor Commencement Date. Tenant further acknowledges
and agrees that neither Landlord nor any agent of Landlord has made any
representation or warranty with respect to the 2Oth Floor Space.

                                       4
<PAGE>
      (f) 20th Floor Allowance. Landlord shall provide to Tenant an improvement
allowance in an amount equal to One Hundred Forty-Nine Thousand Two Hundred Five
Dollars ($149,205.00) ("20th Floor Allowance"), to reimburse Tenant for actual
costs incurred by it in connection with the refurbishment, repair, improvement
and/or alteration of the 20th Floor Space. Any repairs, refurbishment,
improvements or alterations shall be completed by Tenant at its own expense, and
subject to the provisions of Article 10 of the Lease. The 20th Floor Allowance,
or any portion thereof, shall be payable by Landlord as the work progresses
within thirty (30) days following receipt of Tenant's disbursement requests
against such allowance as set forth herein. Such requests shall include the
following items, to the extent applicable to the items for which the 2Oth Floor
Allowance disbursement is being requested: (i) proper receipts for said repairs,
refurbishment, improvements or alterations, or any portions thereof, (ii) a
certification from the contractor performing said work that the sums billed
reflect work actually performed, (iii) executed conditional mechanic's and
materialman's lien releases, in the statutory form, from all parties being paid
from such disbursement, (iv) such other information or documentation as
Landlord may reasonably request.

      (g) Suite 2040 First Offer Right. Tenant shall have a right of first offer
to lease the balance of the space on the 20th floor of the Building in
accordance with the terms and conditions set forth in Rider One attached hereto
and made a part hereof.

4. Security Deposit. Upon Tenant's execution and delivery of this Second
Amendment, Tenant shall deliver and cause to be in effect upon the execution of
this Second Amendment, during the Lease Term, and for a period sixty (60) days
thereafter, an unconditional, irrevocable letter of credit in the amount of
$2,215,863.90 in favor of Landlord ("Letter of Credit"). The cash portion of the
Security Deposit paid by Tenant under the Lease and the Letter of Credit shall
be referred to collectively herein and in the Lease as the "Security Deposit";
notwithstanding anything to the contrary, nothing herein shall affect the
provisions applicable to the letter of credit provided by Tenant under the First
Amendment to Office Lease. The Security Deposit shall serve as security for the
prompt, full and faithful performance by Tenant of the terms and provisions of
the Lease as amended hereby. In accordance with the terms hereof, Tenant shall
deliver the Letter of Credit to Landlord upon the execution of this Second
Amendment. Such Letter of Credit shall be in a form reasonably acceptable to
Landlord and issued by a bank selected by Tenant and reasonably acceptable to
Landlord. Without limiting the generality of the foregoing, any bank issuing the
Letter of Credit shall be a bank that accepts deposits, maintains accounts, has
a local San Francisco office that will negotiate a letter of credit, and the
deposits of which are insured by the Federal Deposit Insurance Corporation. The
Letter of Credit shall provide that the issuing bank shall deliver to Landlord
at least sixty (60) days prior written notice of the termination or expiration
of any such Letter of Credit. Tenant shall pay all expenses, points, or fees
incurred by Tenant in obtaining and maintaining the Letter of Credit. The
Security Deposit shall be held by Landlord as security for the prompt, full and
faithful performance by Tenant of all of the terms, covenants and conditions of
this Lease, and for reimbursement of Landlord of certain expenses incurred by
Landlord in connection with the execution of this Lease. Without limiting the
generality of the foregoing, Tenant acknowledges and agrees that the

                                       5
<PAGE>
Security Deposit may be applied by Landlord, upon the occurrence of a default
(including, without limitation, termination of this Lease following a default)
to reimburse Landlord for (i) the unamortized cost of leasing commissions
payable by Landlord in connection with this Lease, and (ii) the unamortized cost
of the 25th Floor Allowance and the 20th Floor Allowance (collectively, the
"Reimbursable Expenses"). Tenant agrees, upon termination of this Lease or upon
Tenant's default, that Landlord shall have the right to draw upon the cash
portion of the Security Deposit and/or the Letter of Credit, and apply the
proceeds thereof to reimburse Landlord for any unperformed Lease obligations and
any Reimbursable Expenses. in addition, upon the occurrence of a default under
this Lease, Landlord, in its sole and absolute discretion, shall have the right
to draw upon the cash portion of the Security Deposit and/or Letter of Credit
and apply the proceeds to satisfy Tenant's outstanding obligations under the
Lease as amended hereby. The use or application of the Security Deposit or any
portion thereof shall not prevent Landlord from exercising any other right or
remedy provided hereunder or under any Law and shall not be construed as
liquidated damages. If Landlord uses or applies any portion of the Letter of
Credit, Tenant shall, within ten (10) business days after demand, (a) deposit
cash (which shall constitute an additional Security Deposit) with Landlord in an
amount that, when added to the amount remaining under the Letter of Credit,
equals $2,215,863.90, or (b) deliver written documentation executed by the bank
issuing the Letter of Credit that confirms that the Letter of Credit has been
reinstated or a new or additional Letter of Credit issued in such full amount,
and Tenant's failure to do so shall be deemed a material breach of the Lease. If
Landlord uses or applies any portion of the cash portion of the Security
Deposit, Tenant shall, within ten (10) business days after demand, deposit cash
with Landlord in an amount that when added to the remaining cash portion of the
Security Deposit equals $158,404.75. Upon sixty (60) days following expiration
of the Term of the Lease as amended hereby and the vacation of the Premises by
Tenant, other than when a default has occurred, Landlord shall: (i) release the
Letter of Credit and Tenant's obligation to provide the Letter of Credit shall
cease and (ii) return the cash portion of the Security Deposit (without
interest) to Tenant. In addition, Tenant shall have the right, at its sole
expense, to reduce the amount of the Letter of Credit to $1,661,897.90 if and
only if: (i) following the execution hereof, Tenant has achieved positive net
profits for four (4) consecutive quarters as shown on audited financial
statements prepared in accordance with generally accepted accounting principles
consistently applied, and (ii) Tenant has not been in default under this Lease
and has not been notified by Landlord that it is in default under the Lease
immediately prior to the point at which Tenant proposes to so reduce the Letter
of Credit.

5. Expansion. The parties acknowledge and agree the provisions hereof are
intended to satisfy all of the rights and obligations set forth in Rider Three
to the Lease in connection with the expansion of the existing Premises.
Consequently, Rider Three to the Lease is hereby deleted in its entirety.

6. Existing Premises.

      (a) Term. The Expiration Date for the existing Premises is hereby extended
to December 31, 2011, notwithstanding anything to the contrary in the Lease, and
shall

                                       6
<PAGE>
be coterminous with the Term for the 25th Floor Space and the 20th Floor Space.
Article 2(D) of the Lease and Rider Two, providing Tenant with an option to
extend the Term and the terms and conditions therefor, are hereby deleted in
their entirety.

      (b) Base Rent. Tenant shall pay Landlord Base Rent for the existing
Premises as set forth in the Lease, except that commencing January 1, 2005 and
continuing through December 31, 2011 Base Rent for the existing Premises shall
be increased to the sum of $92.00 per rentable square foot of the existing
Premises per year, which shall be equal to an annual Base Rent of $1,189,652.OO
and a monthly Base Rent of $99,137.67.

7. Extension of Lease Term. Tenant's right to extend the Lease Term as set forth
in Rider Two to the Lease shall be applicable to the existing Premises, the 25th
Floor Space and the 20th Floor Space, and any exercise of Tenant's option to
extend the Lease Term shall apply collectively to all such space; Tenant shall
have no right to extend the Term as to only a portion of such space.

8. Temporary Premises. Landlord hereby leases to Tenant and Tenant hereby hires
from Landlord those certain premises on the 2nd floor of the Building (Suite
230) identified on Exhibit D attached hereto and made a part hereof, comprising
2,330 rentable square feet (the "Temporary Premises"), upon the same terms and
conditions set forth in the Lease except as specifically set forth herein. The
lease term for the Temporary Premises shall commence as of the full execution
and delivery hereof and continue until the 25th Floor the Commencement Date or
the 20th Floor Commencement Date, whichever is earlier. Tenant shall pay rent
equal to $85.00 per rentable square foot of the Temporary Premises per year,
which shall be equal to an annual rent of $198,050.OO and a monthly rent of
$16,504.17 per month. Such rent shall be payable commencing as of the
commencement of the term for the Temporary Premises and thereafter on or before
the first day of each month during the remaining term for such space. The rent
shall be prorated for any partial months involved. Tenant further acknowledges
and agrees that it is leasing the Temporary Premises in its present and "as is"
condition and that Landlord is not responsible for making any repairs or
improvements thereto or for providing Tenant with any allowance for the repair,
improvement or refurbishment thereof. The Temporary Premises shall be used for
general office use only and for no other purpose, and Tenant's use thereof shall
otherwise comply with the restrictions and requirements set forth in the Lease.
Notwithstanding anything to the contrary herein, Tenant's leasing of the
Temporary Premises as set forth herein shall terminate if the Lease is
terminated for any reason.

9. Terms and Conditions.

      (a) Except as expressly set forth herein, the terms and conditions of the
Lease shall apply to the 25th Floor Space and the 20th Floor Space, are hereby
incorporated herein and, as of the respective commencement dates applicable
thereto, shall be collectively referred to for purposes of the Lease, as amended
hereby, as the "Premises". Except as expressly set forth herein, the Lease shall
not be affected by this Second Amendment.

                                       7
<PAGE>
      (b) Tenant hereby acknowledges that, as of the date of this Second
Amendment, there are no existing defaults by Landlord in the performance of its
obligations under the Lease, nor to the best of Tenant's knowledge are there now
any facts or conditions which, with notice or lapse of time or both, will become
such a default, and there is no offset, defense, counterclaim or credit against
any rental or other payment due under the Lease.

10. Brokers. The parties acknowledge that they have dealt only with INSIGNIA/ESG
and Landlord's Building representative broker (whose commission, if any, shall
be paid by Landlord pursuant to a separate written agreement) as broker, agent
or finder in connection with the execution of this Second Amendment and the
rights and obligations created hereby. The parties agree to indemnify and hold
each other harmless from all damages, judgments, liabilities and expenses
(including reasonable attorney's fees) arising from any claims or demands of any
other broker, agent or finder not disclosed herein with whom the indemnifying
party (Landlord or Tenant, as the case may be) has dealt or claimed to have
dealt for any commission or fee alleged to be due in connection with its
participation in the procurement of Tenant or the negotiations with Tenant
concerning the space leased hereunder, the Expiration Date extended hereby or
the execution of this Second Amendment to Office Lease.

      IN WITNESS WHEREOF, the parties hereto have executed this Second Amendment
to Office Lease as of the date first above written.

LANDLORD:

PINE STREET INVESTORS I, L.L.C.
a Delaware limited liability company

By:     Walton Street Real Estate Fund I, L.P.,
        a Delaware limited partnership,
        Managing Partner

        By:     Walton Street Managers I, L.P.,
                a Delaware limited partnership,
                General Partner

                By:     WSC Managers I, Inc.,
                        a Delaware corporation,
                        General Partner

                        By: /s/ Howard Brody
                           -------------------------------------
                        Name: Howard Brody
                             -----------------------------------
                        Title: Vice President
                              ----------------------------------

                                       8
<PAGE>
TENANT:

ART TECHNOLOGY GROUP, INC.,
a Delaware corporation

By: /s/ Paul G. Shorthose
   -------------------------------------
Name: Paul G. Shorthose
     -----------------------------------
Title: President/Chief Operating Officer
      ----------------------------------

                                       9
<PAGE>
                                    RIDER ONE

                          Suite 2040 First Offer Right

      Tenant shall have, in accordance with the terms of this Rider One, a
one-time right of first offer to lease Suite 2040, comprising 3,263 rentable
square feet located on the 2Oth floor of the Building, when and if it becomes
available (the "First Offer Right"). The First Offer Right shall terminate upon
the expiration or earlier termination of the initial Term of the Lease in the
event Suite 2040 has not been offered to Tenant as provided herein during such
initial term. Landlord and Tenant acknowledge and agree that Tenants First Offer
Right shall be subject and subordinate to the rights of tenants leasing said
space when the First Offer Right becomes applicable (including, without
limitation, extension options or other rights which may negatively impact or
render unfeasible Tenant's First Offer Right). If Suite 2040, or any portion
thereof, becomes available to lease to the general public during initial Lease
Term, Landlord shall notify Tenant of the availability of such space. Landlord
shall further notify Tenant of Landlord's then current rental rate and other
terms and conditions applicable to such space, which Landlord shall determine in
its sole but reasonable discretion. For a period of ten (10) days following
receipt of Landlord's notice containing such information, Tenant shall have, on
a one-time basis only, the right of first offer to lease the portion of Suite
2040 being offered by Landlord, at the rental rate and on the terms and
conditions set forth in Landlord's notice by delivering irrevocable and
unconditional written notice thereof to Landlord. If Tenant fails to elect to
lease such space within the ten (10) day period, then Landlord shall be entitled
to lease such space to any other party, at any time, on any terms, in Landlord's
sole discretion, and Tenant's First Offer Right shall terminate and be of no
further force and effect. The First Offer Right shall apply only with respect to
the entire portion of Suite 2040 identified by Landlord in its notice, and may
not be exercised with respect to only a portion thereof.

      Tenant's exercise of its First Offer Right shall not operate to cure any
default by Tenant of any of the terms and provisions in the Lease, nor to
extinguish or impair any rights or remedies of Landlord arising by virtue of
such default. The First Offer Right, shall at Landlord's election, be null and
void, if Tenant is in default under the Lease on the date Tenant exercises its
rights hereunder or at any time thereafter and prior to commencement of the
lease for the space covered by the First Offer Right. Such right is personal to
Tenant, if the Lease or Tenant's right to possession of the Premises shall
terminate in any manner whatsoever before Tenant shall exercise the right herein
provided, or if Tenant shall have subleased or assigned all or any portion of
the Premises (other than to a Related Entity as described in Article 17(G) of
the Lease), then immediately upon such termination, sublease or assignment, the
First Offer Right shall simultaneously terminate and become null and void.
Tenant agrees that time is of the essence of this provision.

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