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                                                                   Exhibit 10.15
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                   INTELLECTUAL PROPERTY SECURITY AGREEMENT

                                    BETWEEN

                                NAVISITE, INC.

                                      AND

                                  CMGI, INC.


                ------------------------------------------------


                             Dated as of May 1, 1999


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<PAGE>

                               TABLE OF CONTENTS

                                     Title
                                     -----
Section                                                                     Page
-------                                                                     ----

Recitals..................................................................... 1

Agreement.................................................................... 1

Section 1.  Pledge........................................................... 1

Section 2.  Secured Obligations.............................................. 3

Section 3.  No Release....................................................... 3

Section 4.  Supplements; Further Assurances.................................. 3

Section 5.  Representations and Warranties of Pledgor........................ 4

Section 6.  Covenants........................................................ 5

Section 7.  Transfers and Other Liens........................................ 8

Section 8.  Remedies upon Default............................................ 8

Section 9.  Application of Proceeds.......................................... 9

Section 10.  Expenses........................................................ 9

Section 11.  No Waiver; Cumulative Remedies.................................. 10

Section 12.  The Lender May Perform; the Lender Appointed Attorney-in-Fact... 10

Section 13.  Indemnity....................................................... 10

Section 14.  Litigation...................................................... 12

Section 15.  Modifications in Writing........................................ 12

Section 16.  Termination; Release............................................ 12
<PAGE>

Section 17.  Reinstatement................................................... 13

Section 18.  Notes........................................................... 13

Section 20.  Continuing Security Interest; Assignment........................ 13

Section 21.  Governing Law; Terms............................................ 13

Section 22.  Consent To Jurisdiction and Service of Process.................. 14

Section 23.  Severability of Provisions...................................... 14

Section 24.  Execution in Counterparts....................................... 14

Section 25.  Headings........................................................ 15

Section 26.  Obligations Absolute............................................ 15

Section 27.  Waiver of Single Action......................................... 15

Section 28.  Future Advances................................................. 16




                                   SCHEDULES

         Schedule A   Patents

         Schedule B   Trademarks & Service Marks

         Schedule C   Copyrights

         Schedule D   Liens

         Schedule E   Required Consents & Licenses

         Schedule F   Claims, Litigation, Etc.
<PAGE>

                   INTELLECTUAL PROPERTY SECURITY AGREEMENT

                            Dated as of May 1, 1999

         This INTELLECTUAL PROPERTY SECURITY AGREEMENT (this "Agreement"), is
                                                              ---------
made as of May 1, 1999, by and between NAVISITE, INC. a Delaware corporation
having its principal place of business at One Hundred Brickstone Square,
Andover, Massachusetts 01810 ("Pledgor"), in favor of CMGI, INC., having an
                               -------
office at One Hundred Brickstone Square, Andover, Massachusetts 01810 (the
"Lender").
 ------
                                   RECITALS
                                   --------

     A. The Lender has agreed to make certain advances (the "Loans") to the
                                                             -----
Pledgor, which advances shall be evidenced by a Secured Convertible Demand Note
dated as of May 1, 1999 (the "Convertible Note") and a Secured Demand Note dated
                              ----------------
May 1, 1999 (the "Demand Note," and, together with the Convertible Note, the
                  -----------
"Notes").
 -----

     B. Pledgor is the owner of the Pledged Collateral (as defined below)

     C. It is a condition precedent to the Lender's willingness to make the
Loans that Pledgor shall execute and deliver, among other agreements, this
Agreement.

     D. This Agreement is given by Pledgor in favor of the Lender to secure the
payment and performance of all of the Secured Obligations (as defined below).

     E. This Agreement, the Notes, the Security Agreement between the Lender and
the Pledgor of even date herewith, and all documents executed in connection with
any of the foregoing are collectively referred to herein as the "Loan
                                                                 ----
Documents."
---------
                                   AGREEMENT
                                   ---------

     NOW, THEREFORE, in consideration of the foregoing premises and for other
good and valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, Pledgor and the Lender hereby agree as follows:

     Section 1. Pledge. Pledgor hereby pledges and grants to the Lender a
                ------
continuing first priority security interest in all of Pledgor's right, title and
interest, whether now existing or hereafter

                                       1
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acquired, in and to the following property (collectively, the "Pledged
                                                               -------
Collateral") to secure all of the Secured Obligations:
----------

     (a) Patents issued or assigned to and all patent applications made by
Pledgor and all exclusive licenses to Pledgor from third parties or other rights
to use patents owned by such third parties, including, without limitation, the
patents, patent applications and exclusive licenses listed on Schedule A hereto,
                                                              ----------
along with any and all (1) inventions and improvements described and claimed
therein, (2) reissues, divisions, continuations, extensions and
continuations-in-part thereof, (3) income, royalties, damages, claims and
payments now and hereafter due and/or payable under and with respect thereto,
including, without limitation, damages and payments for past, present or future
infringements thereof, (4) rights to sue for past, present and future
infringements thereof, and (5) any other rights corresponding thereto throughout
the world (collectively, "Patents");
                          -------

     (b) Trademarks (including service marks), federal and state trademark
registrations and applications made by Pledgor (excluding Federal Intent To Use
Applications), common law trademarks and trade names owned by or assigned to
Pledgor, all registrations and applications for the foregoing and all exclusive
licenses from third parties of the right to use trademarks of such third
parties, including, without limitation, the registrations, applications and
exclusive licenses listed on Schedule B hereto, along with any and all (1)
                             ----------
renewals thereof, (2) income, royalties, damages and payments now and hereafter
due and/or payable with respect thereto, including, without limitation, damages,
claims and payments for past or future infringements thereof, (3) rights to sue
for past, present and future infringements thereof, and (4) and any other rights
corresponding thereto throughout the world (collectively, "Trademarks");
                                                           ----------

     (c) Copyrights, registered or unregistered, owned by or assigned to
Pledgor, and all exclusive licenses to Pledgor from third parties to use
copyrights owned by such third parties, including, without limitation, the
registrations, applications and exclusive licenses listed on Schedule C hereto,
                                                             ----------
along with any and all (1) renewals and extensions thereof, (2) income,
royalties, damages, claims and payments now and hereafter due and/or payable
with respect thereto, including, without limitation, damages and payments for
past, present or future infringements thereof, (3) rights to sue for past,
present and future infringements thereof, and (4) and any other rights
corresponding thereto throughout the world (collectively, "Copyrights");
                                                           ----------

     (d) The entire goodwill of Pledgor's business and other general intangibles
(including know-how, trade secrets, customer lists, proprietary information,
inventions, methods, procedures and formulae) connected with the use of and
symbolized by Trademarks of Pledgor; and

     (e) All Proceeds (as defined under the Uniform Commercial Code as in effect
in any relevant jurisdiction (the "UCC") or other relevant law) of any of the
                                   ---
foregoing, and in any event including, without limitation, any and all (1)
proceeds of any insurance, indemnity, warranty or guaranty payable to the Lender
or to Pledgor from time to time with respect to any of the Pledged Collateral,
(2) payments (in any form whatsoever) made or due and payable to Pledgor from
time to time in connection with any requisition, confiscation, condemnation,
seizure or forfeiture of all

                                       2
<PAGE>

or any part of the Pledged Collateral by any governmental authority (or any
person acting on behalf of a governmental authority), (3) instruments
representing amounts receivable in respect of any Patents, Trademarks or
Copyrights, (4) products of the Pledged Collateral and (5) other amounts from
time to time paid or payable under or in connection with any of the Pledged
Collateral. Notwithstanding the foregoing, "Pledged Collateral" shall not
include any rights of Pledgor under any contract, agreement, license or
instrument to the extent that such contract, agreement, license or instrument
prohibits the assignment thereof or grant of a lien therein.

     Section 2. Secured Obligations. The security interest hereby granted shall
                -------------------
secure the due and punctual payment and performance of the following liabilities
and obligations of the Pledgor (herein called the "Secured Obligations"):
                                                   -------------------

          (1) Principal of and premium, if any, and interest on the Loans;

          (2) Any and all obligations of the Pledgor under the Notes; and

          (3) Any and all other obligations of the Pledgor to the Lender,
     whether direct or indirect, absolute or contingent, due or to become due or
     now existing or hereafter arising, including, without limitation, any and
     all other fees, premiums, penalties or other indebtedness of the Pledgor to
     the Lender.

     Section 3. No Release. Nothing set forth in this Agreement shall relieve
                ----------
Pledgor from the performance of any term, covenant, condition or agreement on
Pledgor's part to be performed or observed under or in respect of any of the
Pledged Collateral or from any liability to any person or entity (each a
"Person") under or in respect of any of the Pledged Collateral or impose any
 ------
obligation on the Lender to perform or observe any such term, covenant,
condition or agreement on Pledgor's part to be so performed or observed or
impose any liability on the Lender for any act or omission on the part of
Pledgor relating thereto or for any breach of any representation or warranty on
the part of Pledgor contained in this Agreement or any other Loan Document or
under or in respect of the Pledged Collateral or made in connection herewith or
therewith. The obligations of Pledgor contained in this Section 3 shall survive
the termination of this Agreement and the discharge of Pledgor's other
obligations hereunder and under the other Loan Documents.

     Section 4. Supplements; Further Assurances. Pledgor (1) agrees that it will
                -------------------------------
join with the Lender in executing and, at its own expense, will file and refile,
or permit the Lender to file and refile, such financing statements, continuation
statements and other documents (including, without limitation, this Agreement
and exclusive licenses to use software and other property protected by
copyright), in such offices (including, without limitation, the United States
Patent and Trademark Office, appropriate state trademark offices and the United
States Copyright Office), as the Lender may reasonably deem necessary or
appropriate, wherever required or permitted by law in order to perfect and
preserve the rights and interests granted to the Lender hereunder, and (2)
hereby authorizes the Lender to file financing statements and amendments,
relative to all or any part of the Pledged Collateral, without the signature of
Pledgor where permitted by law and agrees to do such

                                       3
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further acts and things, and to execute and deliver to the Lender such
additional assignments, agreements, powers and instruments, as the Lender may
reasonably require to carry into effect the purposes of this Agreement or better
to assure and confirm unto the Lender its respective rights, powers and remedies
hereunder. Pledgor shall, upon the reasonable request of the Lender, and hereby
authorizes the Lender to, take any and all such actions as may be deemed
advisable by the Lender to perfect and preserve the rights and interests granted
to the Lender with respect to the Pledged Collateral wherever located. All of
the foregoing shall be at the sole cost and expense of Pledgor.

     Section 5. Representations and Warranties of Pledgor. Pledgor hereby
                -----------------------------------------
represents and warrants to the Secured Parties as follows:

     (a) Pledgor is, and, as to Pledged Collateral acquired by it from time to
     time after the date hereof, Pledgor will be, the sole and exclusive owner
     or, as applicable, licensee of all Pledged Collateral, subject to Section
     7. The pledge and security interest created by this Agreement shall not at
     any time be subject to any prior lien, pledge, security interest,
     encumbrance, assignment, collateral assignment or charge of any kind,
     including, without limitation, any filing or agreement to file a financing
     statement as debtor under the UCC or any similar statute or any
     subordination arrangement in favor of any party other than Pledgor
     (collectively, "Liens"). Pledgor further represents and warrants to the
                     -----
     Lender that Schedules A, B and C hereto, respectively, are true, correct
                 --------------------
     and complete lists as of the date hereof of all Patents, registered
     Trademarks and Trademark applications and registered Copyrights and
     Copyright applications owned by Pledgor and that Schedules D, E and F
                                                      --------------------
     hereto are true and correct with respect to the matters set forth therein
     as of the date hereof.

     (b) Pledgor has full corporate power, authority and legal right to pledge
     and grant a security interest in the Pledged Collateral in accordance with
     the terms of this Agreement and this Agreement has been duly and validly
     executed and delivered by Pledgor, constitutes the legal, valid and binding
     obligation of Pledgor, enforceable against Pledgor in accordance with its
     terms, subject to applicable bankruptcy, insolvency, reorganization,
     moratorium or other laws affecting creditors' rights generally and subject
     to general principles of equity, regardless of whether considered in a
     proceeding in equity or at law.

     (c) Except as set forth on Schedule E hereto and except for filings with
                                ----------
     the Patent and Trademark Office, under the UCC and under applicable foreign
     law, no authorization, consent, approval, license, qualification or formal
     exemption from, nor any filing, declaration or registration with, any court
     (other than in connection with the exercise of judicial remedies),
     governmental agency or regulatory authority, or with any securities
     exchange or any other Person is required in connection with (1) the pledge
     by Pledgor of the Pledged Collateral pursuant to this Agreement, or the
     execution, delivery or performance by Pledgor of this Agreement, (2) the
     grant of a security interest (including the priority thereof when the
     appropriate filings have been made and accepted) in, the Pledged Collateral
     by Pledgor in the manner and for the purpose contemplated by this Agreement
     or (3) the exercise of the

                                       4
<PAGE>

rights and remedies of the Lender created hereby.

     (d) Pledgor has made and will continue to make all necessary filings and
     recordations from time to time and use appropriate statutory notice to
     protect its interests in the Pledged Collateral, including, without
     limitation, appropriate recordations of its interests in the Patents and
     Trademarks in the United States Patent and Trademark Office and in
     corresponding offices wherever it does business using such Patents and
     Trademarks throughout the world and its claims to Copyrights in the United
     States Copyright Office, in each case including exclusive licenses and as
     otherwise requested from time to time by the Lender, but in any event all
     in a manner consistent with prudent and commercially reasonable business
     practices.

     (e) Pledgor owns or has rights to use all the Pledged Collateral and all
     rights with respect to any of the foregoing used in, necessary for or
     material to Pledgor's business as currently conducted and as contemplated
     to be conducted pursuant to the Loan Documents. To Pledgor's best
     knowledge, the use of such Pledged Collateral by Pledgor does not infringe
     on the rights of any Person and, except as set forth on Schedule F attached
     hereto, no material claim has been made and remains outstanding that
     Pledgor's use of the Pledged Collateral does or may violate the rights of
     any third person.

     (f) Upon filings and the acceptance thereof in the appropriate offices
     under the UCC and in the United States Patent and Trademark Office and the
     United States Copyright Office, this Agreement will create a valid and duly
     perfected first priority lien and security interest in the United States in
     the Pledged Collateral, subject to no Liens.

     Section 6. Covenants. (a) On a continuing basis, Pledgor will, at the
                ---------
expense of Pledgor, subject to any prior licenses, Liens and restrictions, make,
execute, acknowledge and deliver, and file and record in the proper filing and
recording offices, all such instruments or documents, including, without
limitation, appropriate financing and continuation statements, exclusive
licenses and collateral agreements, and take all such action (limited, as
aforesaid, if applicable) as may reasonably be deemed necessary or appropriate
by the Lender (i) to carry out the intent and purposes of this Agreement, (ii)
to assure and confirm to the Lender the grant or perfection of a security
interest in the Pledged Collateral for the benefit of the Lender, and (iii)
during the continuation of an Event of Default, to enable the Lender to exercise
and enforce their rights and remedies hereunder with respect to any Pledged
Collateral. Without limiting the generality of the foregoing, Pledgor:

                (A) will not enter into any agreement that would impair or
conflict with Pledgor's obligations hereunder;

                (B) will, from time to time, upon the Lender's request, cause
its books and records to be marked with such legends or segregated in such
manner as the Lender may specify and take or cause to be taken such other action
and adopt such procedures as the Lender may specify to give notice or to perfect
the security interest in the Pledged Collateral intended to be conveyed

                                       5
<PAGE>

hereby;

     (C) will, promptly following its becoming aware thereof, notify the Lender
of

         (i)  any materially adverse determination in any proceeding in the
United States Patent and Trademark Office or United States Copyright Office with
respect to any Patent, Trademark or Copyright material to Pledgor's business; or

         (ii) any written claim received, the institution of any proceeding or
any materially adverse determination in any federal, state, local or foreign
court or administrative bodies (other than the U.S. Patent and Trademark Office
or the U.S. Copyright Office) regarding Pledgor's claim of ownership in or right
to use any of the Pledged Collateral, its right to register the Pledged
Collateral, or its right to keep and maintain such registration in full force
and effect;

     (D) will properly maintain and protect the Pledged Collateral to the extent
necessary or appropriate for the conduct of Pledgor's business (as presently
conducted and as contemplated by the Loan Documents) and consistent with
Pledgor's current practice in accordance with applicable statutory requirements;

     (E) will not grant or permit to exist any Lien upon or with respect to the
Pledged Collateral or any portion thereof except Liens in favor of the Lender
for itself and the Lender or as permitted under this Agreement and Liens
permitted by Section 7 hereof, and will not execute any security agreement or
financing statement covering any of the Pledged Collateral except in the name of
the Lender for itself and the Secured Parties or as permitted under this
Agreement;

     (F) except in accordance with prudent and commercially reasonable business
practices, will not permit to lapse or become abandoned, settle or compromise
any pending or future litigation or administrative proceeding with respect to
the Pledged Collateral without the consent of the Lender, or contract for sale
or otherwise dispose of the Pledged Collateral or any portion thereof except
pursuant to Section 7 hereof;

     (G) upon Pledgor obtaining knowledge thereof, will promptly notify the
Lender in writing of any event which may reasonably be expected to materially
adversely affect the value of the Pledged Collateral or any portion thereof, the
ability of Pledgor or the Lender to dispose of the Pledged Collateral or any
portion thereof or the rights and remedies of the Lender in relation thereto
including, without limitation, a levy or threat of levy or any legal process
against the Pledged Collateral or any portion thereof;

     (H) until the Lender exercises its rights to make collection, will
diligently keep commercially reasonable records respecting the Pledged
Collateral;

     (I) subject to the first sentence of this Section 6(a), hereby authorizes
the Lender, in its sole discretion, to file one or more financing or
continuation statements and amendments

                                       6
<PAGE>

thereto, relative to all or any part of the Pledged Collateral without the
signature of Pledgor where permitted by law;

     (J) will furnish to the Lender from time to time statements and amended
schedules further identifying and describing the Pledged Collateral and such
other materials evidencing or reports pertaining to the Pledged Collateral as
the Lender may from time to time reasonably request, all in reasonable detail;

     (K) will pay when due any and all taxes, levies, maintenance fees, charges,
assessments, licenses fees and similar taxes or impositions payable in respect
of the Pledged Collateral, that, if not paid, could result in a material adverse
effect, before the same shall become delinquent or in default, except where (a)
the validity or amount thereof is being contested in good faith by appropriate
proceedings, (b) Pledgor has set aside on its books adequate reserves with
respect thereto in accordance with GAAP and (c) the failure to make payment
pending such contest could not reasonably be expected to result in a material
adverse effect;

     (L) will comply in all material respects with all laws, rules and
regulations applicable to the Pledged Collateral; and

     (M) will deposit with the Lender, at such times as the Lender shall
reasonably request, copies of all source code of all software owned by Pledgor
as the Lender shall request which is material to the operation of Pledgor's
business and such source code copy shall be of the most current version of all
software and shall include all modifications and enhancements thereto and shall
be annotated so as to be easily understood by a software technician of
reasonable proficiency.

   (b) If, before the Secured Obligations shall have been paid and satisfied
in full in cash or cash equivalents, Pledgor shall, (1) obtain any rights to any
additional Pledged Collateral or (2) become entitled to the benefit of any
additional Pledged Collateral or any renewal or extension thereof, including any
reissue, division, continuation, or continuation-in-part of any Patent, or any
improvement on any Patent, the provisions of this Agreement shall automatically
apply thereto and any item enumerated in clause 6(b)(1) or clause 6(b)(2) with
respect to Pledgor shall automatically constitute Pledged Collateral if such
would have constituted Pledged Collateral at the time of execution of this
Agreement, and be subject to the Lien and security interest created by this
Agreement without further action by any party. Pledgor shall, at least once in
each calendar quarter, provide to the Lender written notice of any of the
foregoing. In addition, Pledgor shall, at least once in each calendar quarter,
provide written notice to the Lender of all applications for Patents and all
applications for registration of Trademarks or Copyrights made during the
preceding calendar quarter. Pledgor agrees, promptly following the written
request by the Lender, to confirm the attachment of the lien and security
interest created by this Agreement to any rights described in clause 6(b)(1) or
clause 6(b)(2) above if such would have constituted Pledged Collateral at the
time of execution of this Agreement by execution of an instrument in form
acceptable to the Lender.

     (c) Pledgor authorizes the Lender to modify this Agreement by amending
Schedules

                                       7
<PAGE>

A, B and/or C annexed hereto to include any future Pledged Collateral of
-------------
Pledgor, including, without limitations any of the items listed in Section 6(b).

             (d) Pledgor shall file and prosecute diligently all applications
for Patents, Trademarks or Copyrights now or hereafter pending that would be
useful or beneficial to the businesses of Pledgor to which any such applications
pertain, and to do all acts necessary to preserve and maintain all rights in the
Pledged Collateral unless such Pledged Collateral has become obsolete to
Pledgor's business or otherwise does not merit prosecution, as reasonably
determined by Pledgor consistent with prudent and commercially reasonable
business practices. Any and all costs and expenses incurred in connection with
any such actions shall be borne by Pledgor. Except in accordance with prudent
and commercially reasonable business practices, Pledgor shall not abandon any
right to file a Patent, Trademark or Copyright application or any pending
Patent, Trademark or Copyright application or any Patent, Trademark or Copyright
without the consent of the Lender.

     Section 7. Transfers and Other Liens. Pledgor will not (a) sell, convey,
                -------------------------
assign or otherwise dispose of, or grant any option with respect to, any of the
Pledged Collateral except for licensing in the ordinary course of business or
(b) create or permit to exist any Lien upon or with respect to any of the
Pledged Collateral, except for Liens for taxes, assessments or government
charges or claims the payment of which is not at the time required and inchoate
Liens imposed by law (each of which shall, except to the extent otherwise
required by law, be subordinate to the lien created by this Agreement) and the
lien granted to the Lender under this Agreement.

     Section 8. Remedies upon Default.
                ---------------------
     (a)     If any Event of Default shall have occurred and be continuing, the
Lender may to the full extent permitted by law (1) exercise any and all rights
as beneficial and legal owner of the Pledged Collateral, including, without
limitation, perfecting assignment of any and all contractual rights and powers
with respect to the Pledged Collateral and (2) sell or assign or grant a license
to use, or cause to be sold, assigned or licensed any or all of the Pledged
Collateral (in the case of Trademarks, along with the goodwill associated
therewith) or any part thereof, in each case, free of all rights and claims of
Pledgor therein and thereto. In accordance with such rights, the Lender shall
have (A) the right to cause any or all of the Pledged Collateral to be
transferred of record into the name of the Lender or its nominee and (B) the
right to impose (i) such limitations and restrictions on the sale or assignment
of the Pledged Collateral as the Secured Parties may deem to be necessary or
appropriate to comply with any law, rule or regulation (federal, state or local)
having applicability to the sale or assignment, and (ii) any necessary or
appropriate requirements for any required governmental approvals or consents.

     (b)     Except as provided in this Section 8 and other express notice
provisions of the Loan Documents, Pledgor hereby expressly waives, to the
fullest extent permitted by applicable law, any and all notices, advertisements,
hearings or process of law in connection with the exercise by the Secured
Parties of any of their rights and remedies hereunder.

                                       8
<PAGE>

     (c) Pledgor agrees that, to the extent notice of sale shall be required by
law, ten (10) days' notice from the Lender of the time and place of any public
sale or of the time after which a private sale or other intended disposition is
to take place shall be commercially reasonable notification of such matters. In
addition to the rights and remedies provided in this Agreement and in the other
Loan Documents, the Secured Parties shall have all the rights and remedies of a
secured party under the UCC.

     (d) Except as otherwise provided herein, Pledgor hereby waives, to the
fullest extent permitted by applicable law, notice or judicial hearing in
connection with the Lender's taking possession or the Lender's disposition of
any of the Pledged Collateral, including, without limitation, any and all prior
notice and rights to a hearing for any prejudgment remedy or remedies and any
such right which Pledgor would otherwise have under law, and Pledgor hereby
further waives to the extent permitted by applicable law: (1) all damages
occasioned by any such taking of possession; (2) all other requirements as to
the time, place and terms of sale or other requirements with respect to the
enforcement of the Secured Parties' rights hereunder; and (3) all rights of
redemption, appraisal, valuation, stay, extension or moratorium now or hereafter
in force under any applicable law. Any sale of, or the grant of options to
purchase, or any other realization upon, any Pledged Collateral shall operate to
divest all right, title, interest, claim and demand, either at law or in equity,
of Pledgor therein and thereto, and shall be a perpetual bar both at law and in
equity against Pledgor and against any and all Persons claiming or attempting to
claim the Pledged Collateral so sold, optioned or realized upon, or any part
thereof, from, through or under Pledgor.

     Section 9. Application of Proceeds. The proceeds of any Pledged Collateral
                -----------------------
obtained pursuant to the exercise of any remedy set forth in Section 8 shall be
applied, together with any other sums then held by the Lender pursuant to this
Agreement, promptly by the Lender:

          First, to the payment of all costs and expenses, fees, commissions and
          -----
     taxes of such sale, collection or other realization, including, without
     limitation, reasonable reimbursement to the Lender, and its agents and
     counsel for all expenses, fees, liabilities and advances made or incurred
     by them in connection therewith and all expenses, liabilities and advances
     made or incurred by the Lender in connection therewith, together with
     interest on each such amount at the rate then in effect under the Notes;

          Second, to the payment of all other costs and expenses of such sale,
          ------
     collection or other realization, including, without limitation, reasonable
     reimbursement to the Lender and its agents and counsel for all expenses,
     fees, liabilities and advances made or incurred by them in connection
     therewith and all costs, liabilities and indebtedness made or incurred by
     the Lender in connection therewith together with interest on each such
     amount at the highest rate then in effect under the Notes;

          Third, to the indefeasible payment in full in cash of the Secured
          -----
     Obligations, ratably according to the unpaid amounts thereof, without
     preference or priority of any kind among amounts so due and payable; and

                                       9
<PAGE>

          Fourth, to Pledgor, or its successors or assigns, or to
          ------
     whomsoever may be lawfully entitled to receive the same or as a court
     of competent jurisdiction may direct, of any surplus then remaining
     from such Proceeds.

     Section 10. Expenses. Pledgor will pay on demand all expenses of the Lender
                 --------
and the Secured Parties in connection with the preparation, waiver or amendment
of this Agreement or other Loan Documents executed in connection therewith, or
the administration, default or collection of the Loans or administration,
default, collection in connection with the Lender's exercise, preservation or
enforcement of any of its rights, remedies or options thereunder, including,
without limitation, reasonable fees and disbursements of outside legal counsel
or accounting, consulting, brokerage or other similar professional fees or
expenses, and any fees or expenses associated with any travel or other costs
relating to any appraisals or examinations conducted in connection with the
Secured Obligations or any Collateral therefor, and the amount of all such
expenses shall, until paid, bear interest at the rate applicable to principal
hereunder (including any default rate).

     Section 11. No Waiver; Cumulative Remedies. (a) No failure on the part of
                 ------------------------------
the Lender or the Secured Parties to exercise, no course of dealing with respect
to, and no delay on the part of the Lender in exercising, any right, power or
remedy hereunder shall operate as a waiver thereof; nor shall any single or
partial exercise of any such right, power or remedy hereunder preclude any other
or further exercise thereof or the exercise of any other right, power or remedy.
The remedies herein provided are cumulative and are not exclusive of any
remedies provided by law.

     (b) In the event the Lender shall have instituted any proceeding to enforce
any right, power or remedy under this instrument by foreclosure, sale, entry or
otherwise, and such proceeding shall have been discontinued or abandoned for any
reason or shall have been determined adversely to the Lender, then and in every
such case, Pledgor and the Lender shall, to the extent permitted by applicable
law, be restored to their respective former positions and rights hereunder with
respect to the Pledged Collateral, and all rights, remedies and powers of the
Lender shall continue as if no such proceeding had been instituted.

     Section 12. The Lender May Perform; the Lender Appointed Attorney-in-Fact.
                 -------------------------------------------------------------
If Pledgor shall fail to do any act or thing that it has covenanted to do
hereunder or any warranty on the part of Pledgor contained herein shall be
breached, the Lender may (but shall not be obligated to) do the same or cause it
to be done or remedy any such breach, and may expend funds for such purpose. Any
and all amounts so expended by the Lender shall be paid by Pledgor promptly upon
demand therefor, with interest at the highest rate then in effect under the
Notes during the period from and including the date on which such funds were so
expended to the date of repayment. Pledgor's obligations under this Section 12
shall survive the termination of this Agreement and the discharge of Pledgor's
other obligations hereunder. Pledgor hereby appoints the Lender its attorney-in-
fact with an interest, with full authority in the place and stead of Pledgor and
in the name of Pledgor, or otherwise, from time to time in the Lender's
reasonable discretion to take any action and to execute any instruments
consistent with the terms of this Agreement and the other Loan Documents which
the Lender may deem necessary or advisable to accomplish the purposes of this
Agreement. The

                                       10
<PAGE>

foregoing grant of authority is a power of attorney coupled with an interest and
such appointment shall be irrevocable for the term of this Agreement. Pledgor
hereby ratifies all that such attorney shall lawfully do or cause to be done by
virtue hereof.

     Section 13. Indemnity.
                 ---------

     (a) Indemnity. Pledgor agrees to indemnify, reimburse and hold the Lender
         ---------
and its successors, assigns, employees, agents and servants (collectively,
"Indemnitees") harmless from and against any and all liabilities, obligations,
damages, injuries, penalties, claims, demands, actions, suits, judgments and any
and all costs and expenses (including, without limitation, attorneys' fees and
expenses and the allocated costs of internal counsel) of whatsoever kind and
nature imposed on, asserted against or incurred by any of the Indemnitees in any
way relating to or arising out of this Agreement or the other Loan Documents or
in any other way connected with the administration of the transactions
contemplated hereby or the enforcement of any of the terms hereof, or the
preservation of any rights hereunder, or in any way relating to or arising out
of the manufacture, processing, ownership, ordering, purchase, delivery,
control, acceptance, lease, financing, possession, operation, condition, sale,
return or other disposition, or use of the Pledged Collateral (including,
without limitation, latent or other defects, whether or not discoverable, any
claim for patent, trademark, trade secret or copyright infringement), the
violation of the laws of any country, state or other governmental body or unit,
any tort (including, without limitation, claims arising or imposed under the
doctrine of strict liability, or for or on account of injury to or the death of
any Person (including any Indemnitee)), or property damage, or contract claim;
provided that Pledgor shall have no obligation to an Indemnitee hereunder to the
extent it is finally judicially determined that such indemnified liabilities
arise solely from the gross negligence or willful misconduct of that Indemnitee.
Upon written notice by any Indemnitee of the assertion of such a liability,
obligation, damage, injury, penalty, claim, demand, action, judgment or suit,
Pledgor shall assume full responsibility for the defense thereof. If any action,
suit or proceeding arising from any of the foregoing is brought against any
Indemnitee, Pledgor shall, if requested by such Indemnitee, resist and defend
such action, suit or proceeding or cause the same to be resisted and defended by
counsel reasonably satisfactory to such Indemnitee. Each Indemnitee shall,
unless any other Indemnitee has made the request described in the preceding
sentence and such request has been complied with, have the right to employ its
own counsel (or internal counsel) to investigate and control the defense of any
matter covered by the indemnity set forth in this Section 13 and the fees and
expenses of such counsel shall be paid by Pledgor; provided that, only to the
extent that no conflict exists between or among the Indemnitees as reasonably
determined by the Indemnitees, Pledgor shall not be obligated to pay the fees
and expenses of more than one counsel for all Indemnitees as a group with
respect to any such matter, action, suit or proceeding.

     (b) Misrepresentations. Without limiting the application of subsection
         ------------------
13(a), Pledgor agrees to pay, indemnify and hold each Indemnitee harmless from
and against any loss, costs, damages and expenses which such Indemnitee may
suffer, expend or incur in consequence of or growing out of any
misrepresentation by Pledgor in this Agreement or any of the other Loan
Documents or in any statement or writing contemplated by or made or delivered
pursuant to or in

                                       11
<PAGE>

connection with this Agreement or any of the other Loan Documents.

     (c) Contribution. If and to the extent that the obligations of Pledgor
         ------------
under this Section 13 are unenforceable for any reason, Pledgor hereby agrees to
make the maximum contribution to the payment and satisfaction of such
obligations that is permissible under applicable law.

     (d) Survival. The obligations of Pledgor contained in this Section 13 shall
         --------
survive the termination of this Agreement and the discharge of Pledgor's other
obligations hereunder and under the other Loan Documents.

     (e) Reimbursement. Any amounts paid by any Indemnitee as to which such
         -------------
Indemnitee has the right to reimbursement shall constitute Secured Obligations
secured by the Pledged Collateral.

     Section 14. Litigation.
                 ----------

     (a) Pledgor shall have the right to commence and prosecute in its own name,
as real party in interest, for its own benefit and at its own expense, such
applications for protection of Pledged Collateral, suits, proceedings or other
actions for infringement, counterfeiting, unfair competition, dilution or other
damage as are in its reasonable business judgment necessary to protect the
Pledged Collateral. Pledgor shall promptly notify the Lender in writing as to
the commencement and prosecution of any such actions, or threat thereof relating
to the Pledged Collateral and shall provide to the Lender such information with
respect thereto as may be reasonably requested. The Lender shall provide all
reasonable and necessary cooperation in connection with any such suit,
proceeding or action, including, without limitation, joining as a necessary
party.

     (b) Upon the occurrence and during the continuation of an Event of Default,
the Lender shall have the right but shall in no way be obligated to file
applications for protection of the Pledged Collateral and/or bring suit in the
name of Pledgor or the Lender to enforce the Pledged Collateral and any license
thereunder; in the event of such suit, Pledgor shall, at the request of the
Lender, do any and all lawful acts and execute any and all documents required by
the Lender in aid of such enforcement and Pledgor shall promptly, upon demand,
reimburse and indemnify the Lender, as the case may be, for all costs and
expenses incurred by the Lender in the exercise of its rights under this Section
14. In the event that the Lender shall elect not to bring suit to enforce the
Pledged Collateral, Pledgor agrees to use all reasonable measures, whether by
action, suit, proceeding or otherwise, to prevent the infringement,
counterfeiting or other diminution in value of any of the Pledged Collateral by
others and for that purpose agrees to diligently maintain any action, suit or
proceeding against any person so infringing necessary to prevent such
infringement as is in the reasonable business judgment of Pledgor necessary to
protect the Pledged Collateral and the Lender shall provide, at Pledgor's
expense, all necessary and reasonable assistance to Pledgor to maintain such
action.

     Section 15. Modifications in Writing. No amendment, modification,
                 ------------------------
supplement,

                                       12
<PAGE>

termination or waiver of or to any provision of this Agreement, nor consent to
any departure by Pledgor therefrom, shall be effective unless the same shall be
in writing and signed by the Lender and, except in the case of any such
termination, waiver or consent, by the Pledgor. Any amendment, modification or
supplement of or to any provision of this Agreement, any waiver of any provision
of this Agreement, and any consent to any departure by Pledgor from the terms of
any provision of this Agreement, shall be effective only in the specific
instance and for the specific purpose for which made or given. Except where
notice is specifically required by this Agreement or any other Loan Document, no
notice to or demand on Pledgor in any case shall entitle Pledgor to any other or
further notice or demand in similar or other circumstances.

     Section 16. Termination; Release. When all the Secured Obligations (other
                 --------------------
than Secured Obligations in the nature of continuing indemnitees or expense
reimbursement obligations not yet due and payable) have been paid in full and
have been terminated and the Lender and the Pledgor agree to terminate this
Agreement, this Agreement shall terminate. Upon termination of this Agreement,
the Lender shall, upon the request and at the expense of Pledgor, forthwith
assign, transfer and deliver to Pledgor against receipt and without recourse to
or warranty by the Lender, such of the Pledged Collateral to be released (in the
case of a release) as may be in the possession of the Lender and as shall not
have been sold or otherwise applied pursuant to the terms hereof, on the order
of and at the expense of Pledgor, and proper instruments (including UCC
termination statements on Form UCC-3 and documents suitable for recordation in
the United States Patent and Trademark Office, the United States Copyright
Office or similar domestic or foreign authority) acknowledging the termination
of this Agreement or the release of such Pledged Collateral, as the case may be.

     Section 17. Reinstatement. Notwithstanding the provisions of Section 16,
                 -------------
this Agreement shall continue to be effective or be reinstated, as the case may
be, if at any time any amount received by the Lender in respect of the Secured
Obligations is rescinded or must otherwise be restored or returned by the Lender
upon the insolvency, bankruptcy, dissolution, liquidation or reorganization of
Pledgor or upon the appointment of any intervenor or conservator of, or trustee
or similar official for, Pledgor or any substantial part of its properties, or
otherwise, all as though such payments had not been made.

     Section 18. Notes. Notwithstanding any other provision of this Agreement,
                 -----
the rights of the parties hereunder are subject to the provisions of the Notes,
including the provisions thereof pertaining to the rights and responsibilities
of the Lender.

     Section 19. Notices. All notices, consents, approvals, elections and other
                 -------
communications hereunder shall be in writing (whether or not the other
provisions of this Agreement expressly so provide) and shall be deemed to have
been duly given if delivered by hand or overnight courier service, mailed by
certified or registered mail or sent by telephonic facsimile (fax), as follows:
(i) if to the Lender, to CMGI, Inc., 100 Brickstone Square, Andover,
Massachusetts 01810, Attention: Chief Financial Officer, and (ii) if to the
Debtor, to NaviSite, Inc., 100 Brickstone Square, Andover, Massachusetts 01810,
Attention: Chief Financial Officer.

                                       13
<PAGE>

     Section 20. Continuing Security Interest; Assignment. This Agreement shall
                 ----------------------------------------
create a continuing security interest in the Pledged Collateral and shall (a)
remain in full force and effect until the payment in full in cash of all Secured
Obligations, (b) be binding upon Pledgor, its successors and assigns, and (c)
inure, together with the rights and remedies of the Secured Parties hereunder,
to the benefit of the Lender and its successors, transferees and assigns; no
other Persons (including, without limitation, any other creditor of Pledgor)
shall have any interest herein or any right or benefit with respect hereto.
Without limiting the generality of the foregoing clause 20(c), any the Lender
may assign or otherwise transfer any indebtedness held by it secured by this
Agreement to any other Person, and such other Person shall thereupon become
vested with all the benefits in respect thereof granted to the Lender, herein or
otherwise, subject however, to the provisions of the Notes.

     Section 21. GOVERNING LAW; TERMS. THIS AGREEMENT SHALL BE GOVERNED BY, AND
                 --------------------
SHALL BE CONSTRUED AND ENFORCED IN ACCORDANCE WITH, THE LAWS OF THE COMMONWEALTH
OF MASSACHUSETTS, WITHOUT REGARD TO PRINCIPLES OF CONFLICTS OF LAW, EXCEPT TO
THE EXTENT THAT THE VALIDITY OR PERFECTION OF THE INTEREST HEREUNDER, OR
REMEDIES HEREUNDER IN RESPECT OF ANY PARTICULAR INTELLECTUAL PROPERTY ARE
GOVERNED BY THE LAWS OF A JURISDICTION OTHER THAN THE COMMONWEALTH OF
MASSACHUSETTS.

     Section 22. CONSENT TO JURISDICTION AND SERVICE OF PROCESS. ALL JUDICIAL
                 ----------------------------------------------
PROCEEDINGS BROUGHT AGAINST PLEDGOR WITH RESPECT TO THIS AGREEMENT MAY BE
BROUGHT IN ANY STATE OR FEDERAL COURT OF COMPETENT JURISDICTION IN THE
COMMONWEALTH OF MASSACHUSETTS AND BY EXECUTION AND DELIVERY OF THIS AGREEMENT,
PLEDGOR ACCEPTS FOR ITSELF AND IN CONNECTION WITH ITS PROPERTIES, GENERALLY AND
UNCONDITIONALLY THE NONEXCLUSIVE JURISDICTION OF THE AFORESAID COURTS AND
IRREVOCABLY AGREES TO BE BOUND BY ANY JUDGMENT RENDERED THEREBY IN CONNECTION
WITH THIS AGREEMENT. THE PARTIES HERETO HEREBY IRREVOCABLY WAIVE TRIAL BY JURY,
AND PLEDGOR HEREBY IRREVOCABLY WAIVES ANY OBJECTION, INCLUDING, WITHOUT
LIMITATION, ANY OBJECTION TO THE LAYING OF VENUE OR BASED ON THE GROUNDS OF
FORUM NON CONVENIENS, WHICH IT MAY NOW OR HEREAFTER HAVE TO THE BRINGING OF ANY
SUCH ACTION NOR PROCEEDING IN SUCH RESPECTIVE JURISDICTIONS. IN THE EVENT THAT
PLEDGOR DESIGNATES AND APPOINTS ANY PERSON AS ITS AGENTS AND SUCH PERSON
IRREVOCABLY AGREES IN WRITING TO SERVE AS PLEDGOR'S AGENT TO RECEIVE ON
PLEDGOR'S BEHALF SERVICE OF ALL PROCESS IN ANY SUCH PROCEEDINGS IN ANY SUCH
COURT, SUCH SERVICE IS HEREBY ACKNOWLEDGED BY PLEDGOR TO BE EFFECTIVE AND
BINDING SERVICE IN EVERY RESPECT. A COPY OF SUCH PROCESS SO SERVED SHALL BE
MAILED BY REGISTERED MAIL TO PLEDGOR, AND PLEDGOR HEREBY AGREES THAT SERVICE
UPON IT BY MAIL CONSTITUTES SUFFICIENT NOTICE. NOTHING HEREIN SHALL AFFECT THE
RIGHT TO SERVE PROCESS IN ANY OTHER

                                       14
<PAGE>

MANNER PERMITTED BY LAW OR SHALL LIMIT THE RIGHT OF THE LENDER TO BRING
PROCEEDINGS AGAINST PLEDGOR IN THE COURTS OF ANY OTHER JURISDICTION.

     Section 23. Severability of Provisions. Any provision of this Agreement
                 --------------------------
which is prohibited or unenforceable in any jurisdiction shall, as to such
jurisdiction, be ineffective to the extent of such prohibition or
unenforceability without invalidating the remaining provisions hereof or
affecting the validity or enforceability of such provision in any other
jurisdiction.

     Section 24. Execution in Counterparts. This Agreement and any amendments,
                 -------------------------
waivers, consents or supplements hereto may be executed in any number of
counterparts and by different parties hereto in separate counterparts, each of
which when so executed and delivered shall be deemed to be an original, but all
such counterparts together shall constitute one and the same agreement.

     Section 25. Headings. The Section headings used in this Agreement are for
                 --------
convenience of reference only and shall not affect the construction of this
Agreement.

     Section 26. Obligations Absolute. To the extent permitted by applicable
                 --------------------
law, all obligations of Pledgor hereunder shall be absolute and unconditional
irrespective of:

     (a) any bankruptcy, insolvency, reorganization, arrangement, readjustment,
composition liquidation or the like of Pledgor or any other subsidiary of
Pledgor;

     (b) any lack of validity or enforceability of the Notes, any other Loan
Document, or any other agreement or instrument relating thereto;

     (c) any change in the time, manner or place of payment of, or in any other
term of, all or any of the Secured Obligations, or any other amendment or waiver
of or any consent to any departure from the Notes, any other Loan Document, or
any other agreement or instrument relating thereto;

     (d) any exchange, release or non-perfection of any other collateral, or any
release or amendment or waiver of or consent to any departure from any
guarantee, for all or any of the Secured Obligations; or

     (e) any exercise or non-exercise, or any waiver of any right, remedy, power
or privilege under or in respect of this Agreement or any other Loan Document
except as specifically set forth in a waiver granted pursuant to the provisions
of Section 15 hereof.

     Section 27. Waiver of Single Action. Pledgor hereby waives to the greatest
                 -----------------------
extent permitted under law the right to a discharge of any of the Secured
Obligations under any statute or rule of law now or hereafter in effect which
provides that the exercise of any particular right or

                                       15
<PAGE>

remedy as provided for herein (by judicial proceedings or otherwise) constitutes
the exclusive means for satisfaction of the Secured Obligations or which makes
unavailable any further judgment or any other right or remedy provided for
herein because the Lender elected to proceed with the exercise of such initial
right or remedy or because of any failure by the Lender to comply with laws that
prescribe conditions to the entitlement to such subsequent judgment or the
availability of such subsequent right or remedy. In the event that,
notwithstanding the foregoing waiver, any court shall for any reason hold that
such subsequent judgment or action is not available to the Lender, Pledgor shall
not (a) introduce in any other jurisdiction any judgment so holding as a defense
to enforcement against Pledgor of any remedy in the Notes or executed in
connection with the Notes or (b) seek to have such judgment recognized or
entered in any other jurisdiction, and any such judgment shall in all events be
limited in application only to the state or jurisdiction where rendered and only
with respect to the collateral referred to in such judgment.

     Section 28. Future Advances. This Agreement shall secure the payment of any
                 ---------------
amounts advanced from time to time pursuant to the Notes.

     Section 29. Construction in Event of Conflict. Simultaneously with the
                 ---------------------------------
execution of this Agreement, the parties are entering into a Security Agreement
(the "Security Agreement"). In the event of any conflict between this Agreement
      ------------------
and the Security Agreement, the terms of this Agreement shall control.

                                       16
<PAGE>

     IN WITNESS WHEREOF, the parties hereto have executed this Agreement as a
sealed instrument as of the date first above written.

                                        NAVISITE, INC.


                                        By: /s/ Joel B. Rosen
                                           -----------------------------------
                                            Name:   Joel B. Rosen
                                            Title:  Chief Executive Officer


                                        CMGI, INC.


                                        By: /s/ Andrew J. Hajducky
                                           -----------------------------------
                                            Name:   Andrew J. Hajducky III
                                            Title:  Chief Financial Officer
<PAGE>

                                  SCHEDULE A

                                    PATENTS
                        (including exclusive licenses)

None.
<PAGE>

                                  SCHEDULE B

                          TRADEMARKS & SERVICE MARKS
       (including registrations and applications and exclusive licenses)

--------------------------------------------------------------------------------
Trademark Name                                     Application/Registration No.
--------------------------------------------------------------------------------
IF INTERNET IS BUSINESS CRITICAL TO YOU ... THEN   75/455172
NAVISITE IS CRITICAL TO YOUR BUSINESS (USA)
--------------------------------------------------------------------------------
NAVICENTER (USA)                                   75/393976
--------------------------------------------------------------------------------
NAVISITE (Canada)                                    1005557
--------------------------------------------------------------------------------
NAVISITE (USA)                                     75/471414
--------------------------------------------------------------------------------
NAVISITE (USA)                                     75/629506
--------------------------------------------------------------------------------
NAVISITE & Design (Canada)                           1005558
--------------------------------------------------------------------------------
NAVISITE & Design (USA)                            75/629096
--------------------------------------------------------------------------------
NAVISITE & Design (USA)                            75/455179
--------------------------------------------------------------------------------
ONLINE SUCCESS FOR REAL WORLD BUSINESS (USA)       75/676153
--------------------------------------------------------------------------------
PROAPPS (Canada)                                     1005560
--------------------------------------------------------------------------------
PROAPPS (USA)                                      75/624506
--------------------------------------------------------------------------------
SERVERCAST (USA)                                   75/255207
--------------------------------------------------------------------------------
SITEHARBOR (Canada)                                  1005559
--------------------------------------------------------------------------------
SITEHARBOR (USA)                                     2217459
--------------------------------------------------------------------------------
YOU MANAGE THE BUSINESS ... WE'LL MANAGE THE         2226213
WEB (USA)
--------------------------------------------------------------------------------

<PAGE>

                                  SCHEDULE C

                                  COPYRIGHTS

       (including registrations and applications and exclusive licenses)


None.
<PAGE>

                                  SCHEDULE D

                                     LIENS

From time to time, the Pledgor has granted a security interest in certain
equipment leased from third parties and used in Pledgor's business to the
financiers of the leases of such equipment.

<PAGE>

                                  SCHEDULE E

                        REQUIRED CONSENTS AND LICENSES


None.
<PAGE>

                                  SCHEDULE F

                           CLAIMS, LITIGATION, ETC.


The Company has received communications from International Business Machines
Corporation ("IBM") and National Semiconductor Corporation ("NSC") alleging
respectively, that the Company has infringed on the IBM mark, "e-business," and
the NSC company logo, a stylized "N". In neither case has a claim been filed
against the Company. The Company has investigated these allegations and believes
that they are without merit.