VOTING AGREEMENT

      This Voting Agreement (the “Agreement”) is made and entered into as of August 10, 2004, between Art Technology, Inc., a Delaware corporation (“Parent”), and the undersigned shareholder (“Shareholder”) of Primus Knowledge Solutions, Inc., a Washington corporation (the “Company”).

RECITALS

      A. Concurrently with the execution of this Agreement, Parent, the Company and Autobahn Acquisition, Inc., a Washington corporation and a wholly-owned subsidiary of Parent (“Merger Sub”), are entering into an Agreement and Plan of Merger (the “Merger Agreement”) which provides for the merger of Merger Sub with and into the Company (the “Merger”). Pursuant to the Merger, shares of common stock of the Company, par value $0.025 per share (“Company Common Stock”) will be converted into shares of Parent Common Stock on the basis described in the Merger Agreement. Capitalized terms used but not defined herein shall have the meanings set forth in the Merger Agreement.

      B. Shareholder is the record holder of such number of outstanding shares of Company Common Stock as is indicated on the final page of this Agreement.

      C. As a material inducement to enter into the Merger Agreement, Parent desires Shareholder to agree, and Shareholder is willing to agree, to vote the Shares (as defined below), and such other shares of capital stock of the Company over which Shareholder has voting power, so as to facilitate consummation of the Merger.

      In consideration of the foregoing and the representations, warranties, covenants and agreements set forth in this Agreement, the parties agree as follows:

      1.     Agreement To Vote Shares.

      1.1     Definitions. For purposes of this Agreement:

      (a) Shares. The term “Shares” shall mean all issued and outstanding shares of Company Common Stock owned of record or beneficially by Shareholder or over which Shareholder exercises voting power, in each case, as of the record date for persons entitled to receive notice of, and to vote at the meeting of the shareholders of the Company called for the purpose of voting on the matters referred to in Section 1.2. Shareholder agrees that any shares of capital stock of the Company that Shareholder purchases or with respect to which Shareholder otherwise acquires beneficial ownership or over which Shareholder exercises voting power after the execution of this Agreement and prior to the date of termination of this Agreement pursuant to Section 3 below shall be subject to the terms and conditions of this Agreement to the same extent as if they constituted Shares on the date hereof.

      (b) Subject Securities. The term “Subject Securities” shall mean: (i) all securities of the Company (including all shares of Company Common Stock and all options, warrants and other rights to acquire shares of Company Common Stock) beneficially owned by Shareholder as of the date of this Agreement; and (ii) all additional securities of the Company (including all additional shares of Company Common Stock and all additional options, warrants and other rights to acquire shares of Company Common Stock) of which Shareholder acquires ownership during the period from the date of this Agreement through the earlier of termination of this Agreement pursuant to Section 3 below or the record date for the meeting at which stockholders of the Company are asked to vote upon approval of the Merger Agreement and the Merger.

      (c) Transfer. Shareholder shall be deemed to have effected a “Transfer” of a security if Shareholder directly or indirectly: (i) sells, pledges, encumbers, transfers or disposes of, or grants an option with respect to, such security or any interest in such security; or (ii) enters into an agreement or commitment providing for the sale, pledge, encumbrance, transfer or disposition of, or grant of an option with respect to, such security or any interest therein.

      1.2     Agreement to Vote Shares. Shareholder hereby covenants and agrees that, during the period commencing on the date hereof and continuing until the first to occur of (i) such date and time as the Merger shall become effective in accordance with the terms and provisions of the Merger Agreement (the “Effective Time”) and (ii) termination of this Agreement in accordance with its terms, at any meeting (whether annual or special and whether or not an adjourned or postponed meeting) of the shareholders of the Company, however called Shareholder will appear at the meeting or otherwise cause the Shares to be counted as present thereat for purposes of establishing a quorum and vote (or cause to be voted) the Shares:

      (1) in favor of the approval and adoption of the Merger Agreement and the approval of the Merger and the other actions contemplated by the Merger Agreement and any actions required in furtherance thereof; and

      (2) against approval of any proposal made in opposition to or in competition with the consummation of the Merger, including, without limitation, any Acquisition Proposal or Superior Offer (each as defined in the Merger Agreement) or any action or agreement that would result in a breach in any respect of any covenant, representation or warranty or any other obligation or agreement of the Company under the Merger Agreement or of Shareholder under this Agreement.

      Shareholder further agrees not to enter into any agreement or understanding with any person the effect of which would be inconsistent with or violative of any provision contained in this Section 1.2.

      1.3     Transfer and Other Restrictions.

      (a) Prior to the termination of this Agreement, Shareholder agrees not to, directly or indirectly:

      (i) except pursuant to the terms of the Merger Agreement, offer for sale, Transfer or otherwise dispose of, or enter into any contract, option or other arrangement or understanding with respect to or consent to the offer for sale Transfer or other disposition of any or all of the Subject Securities or any interest therein except as provided in Section 1.2 hereof;

      (ii) grant any proxy, power of attorney, deposit any of the Subject Securities into a voting trust or enter into a voting agreement or arrangement with respect to the Subject Securities except as provided in this Agreement; or

      (iii) take any other action that would make any representation or warranty of Shareholder contained herein untrue or incorrect or have the effect of preventing or disabling Shareholder from performing its obligations under this Agreement.

      (b) To the extent Shareholder is, as of the date hereof, party to a contract or agreement that requires Shareholder to Transfer Shares to another person or entity (excluding a contract or agreement pledging Shares to the Company), Shareholder will not effect any such Transfer unless and until the transferee agrees to be bound by and executes an agreement in the form of this Agreement with respect to the Shares to be Transferred.

      1.4     Irrevocable Proxy. Concurrently with the execution of this Agreement, Shareholder agrees to deliver to Parent a proxy in the form attached hereto as Exhibit I (the “Proxy”), which shall be irrevocable, with respect to the Shares, subject to the other terms of this Agreement.

      2.     Representations and Warranties of Shareholder.

      (a) Shareholder is the record and beneficial owner of, or Shareholder exercises voting power over, the shares of Company Common Stock indicated on the final page of this Agreement, which, on and as of the date hereof, are free and clear of any Encumbrances that would adversely affect the ability of Shareholder to carry out the terms of this Agreement. The number of Shares set forth on the signature pages hereto are the only Shares beneficially owned by such Shareholder and, except as

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set forth on such signature pages, the Shareholder holds no options or warrants to purchase or rights to subscribe for or otherwise acquire any securities of the Company and has no other interest in or voting rights with respect to any securities of the Company.

      (b) Shareholder has the requisite capacity, power and authority to enter into this Agreement and to consummate the transaction contemplated by this Agreement. The execution and delivery of this Agreement by Shareholder and the consummation by Shareholder of the transactions contemplated by this Agreement have been duly authorized by all necessary action. This Agreement has been duly executed and delivered by Shareholder and constitutes a valid and binding obligation of Shareholder, enforceable against Shareholder in accordance with its terms, except (i) as the same may be limited by applicable bankruptcy, insolvency, moratorium or similar laws of general application relating to or affecting creditors’ rights, and (ii) for the limitations imposed by general principles of equity. If this Agreement is being executed in a representative or fiduciary capacity, the person signing this Agreement has full power and authority to enter into and perform such Agreement. Prior to the approval of the Company’s Board of Directors of this Agreement, Shareholder and Parent had no agreement, arrangement or understanding with respect to the voting of any of Shareholder’s securities of the Company.

      3.     Termination. This Agreement shall terminate and shall have no further force or effect as of the first to occur of (i) the Effective Time and (ii) such date and time as the Merger Agreement shall have been validly terminated pursuant to Article 7 thereof.

      4.     Miscellaneous.

      4.1     Severability. If any term, provision, covenant or restriction of this Agreement is held by a court of competent jurisdiction to be invalid, void or unenforceable, then the remainder of the terms, provisions, covenants and restrictions of this Agreement shall remain in full force and effect and shall in no way be affected, impaired or invalidated.

      4.2     Binding Effect and Assignment. This Agreement and all of the provisions hereof shall be binding upon and inure to the benefit of the parties hereto and their respective successors and permitted assigns, but, except as otherwise specifically provided herein, neither this Agreement nor any of the rights, interests or obligations of the parties hereto may be assigned by either of the parties without the prior written consent of the other. Any purported assignment in violation of this Section shall be void.

      4.3     Amendments and Modification. This Agreement may not be modified, amended, altered or supplemented except upon the execution and delivery of a written agreement executed by the parties hereto.

      4.4     Specific Performance; Injunctive Relief; Attorneys Fees. The parties hereto acknowledge that Parent will be irreparably harmed and that there will be no adequate remedy at law for a violation of any of the covenants or agreements of Shareholder set forth herein. Therefore, it is agreed that, in addition to any other remedies that may be available to Parent upon any such violation, Parent shall have the right to enforce such covenants and agreements by specific performance, injunctive relief or by any other means available to Parent at law or in equity.

      4.5     Notices. All notices and other communications hereunder shall be in writing and shall be deemed duly given upon delivery either by commercial delivery service, or sent via facsimile (receipt

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confirmed) to the parties at the following address or facsimile numbers (or at such other address or facsimile numbers for a party as shall be specified by like notice):

If to Parent:

Art Technology, Inc.
25 First Street
Cambridge, MA 02141
Facsimile: (617) 386-1111
Attention: Chief Executive Officer

with a copy to:

Foley Hoag LLP
Seaport World Trade Center West
155 Seaport Boulevard
Boston, Massachusetts 02210
Facsimile: (617) 832-7000
Attention: John D. Patterson, Jr. and Robert W. Sweet, Jr.

If to Shareholder, to the address for notice set forth on the last page hereof.

with a copy to:

Preston Gates & Ellis LLP
925 Fourth Avenue, Suite 2900
Seattle, Washington 98104-1158
Facsimile: (206) 623-7022
Attention:  Gary J. Kocher and Christopher H. Cunningham

Any party hereto may by notice so given provide and change its address for future notices hereunder.

      4.6     Governing Law. This Agreement shall be governed by and construed exclusively in accordance with the laws of the State of Washington, excluding that body of law relating to conflict of laws.

      4.7     Entire Agreement. The Merger Agreement, this Agreement and the Proxy granted hereunder constitute and contain the entire agreement and understanding of the parties with respect to the subject matter hereof and supersede any and all prior negotiations, correspondence, agreements, understandings, duties or obligations between the parties respecting the subject matter hereof.

      4.8     Counterparts. This Agreement may be executed in counterparts, each of which shall be deemed an original, but all of which together shall constitute one and the same instrument.

      4.9     Captions. The captions to sections of this Agreement have been inserted only for identification and reference purposes and shall not be used to construe or interpret this Agreement.

*     *     *     *     *

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      IN WITNESS WHEREOF, the parties hereto have caused this Voting Agreement to be executed as of the date first above written.

ART TECHNOLOGY, INC.

By: 

Name:        

Title:

SHAREHOLDER:

[ _______________________________________]

                              (Shareholder Name)

Shareholder’s Address for Notice:

Attention:

Outstanding Shares of Company Common

Stock Beneficially Owned by Shareholder:

Options, Warrants or Rights to purchase

Company Common Stock Beneficially Owned

by Shareholder:

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Exhibit I

IRREVOCABLE PROXY

      The undersigned stockholder (the “Shareholder”) of Primus Knowledge Solutions, Inc., a Washington corporation (the “Company”), hereby irrevocably appoints and constitutes each of Robert D. Burke and Edward Terino (collectively, the “Proxyholders”), the agents, attorneys-in-fact and proxies of the undersigned, with full power of substitution and resubstitution, to the full extent of the undersigned’s rights with respect to the shares of capital stock of the Company which are listed below (the “Shares”), and any and all other shares or securities issued or issuable in respect thereof on or after the date hereof and prior to the date this proxy terminates, to vote the Shares as follows: the Proxyholders named above are empowered at any time prior to termination of this proxy to exercise all voting and other rights (including, without limitation, the power to execute and deliver written consents with respect to the Shares) of the undersigned at every annual, special or adjourned meeting of the Company stockholders, and in every written consent in lieu of such a meeting, or otherwise, (i) in favor of adoption of the Agreement and Plan of Merger (the “Merger Agreement”) among Art Technology, Inc., a Delaware corporation (“Parent”), Autobahn Acquisition, Inc., a Washington corporation and wholly-owned subsidiary of Parent (“Merger Sub”) and the Company, and the approval of the merger of Merger Sub with and into the Company (the “Merger”), and (ii) against approval of any proposal made in opposition to or in competition with consummation of the Merger, including, without limitation, any Acquisition Proposal or Superior Offer (each as defined in the Merger Agreement) or any action or agreement that would result in a breach in any respect of any covenant, representation or warranty or any other obligation or agreement of the Company under the Merger Agreement or of the Shareholder under that certain Voting Agreement, dated as of August 10, 2004, by and between Parent and the Shareholder (the “Voting Agreement”).

      The Proxyholders may not exercise this proxy on any other matter. The Shareholder may vote the Shares on all matters other than those set forth in the immediately preceding paragraph. The proxy granted by the Shareholder to the Proxyholders hereby is granted as of the date of this Irrevocable Proxy in order to secure the obligations of the Shareholder set forth in Section 1 of the Voting Agreement, and is irrevocable and coupled with an interest in such obligations and in the interests in the Company to be purchased and sold pursuant to the Merger Agreement.

      This proxy will terminate upon the termination of the Voting Agreement in accordance with its terms. Upon the execution hereof, all prior proxies given by the undersigned with respect to the Shares and any and all other shares or securities issued or issuable in respect thereof on or after the date hereof are hereby revoked and no subsequent proxies will be given until such time as this proxy shall be terminated in accordance with its terms. Any obligation of the undersigned hereunder shall be binding upon the successors and assigns of the undersigned. The undersigned Shareholder authorizes the Proxyholders to file this proxy and any substitution or revocation of substitution with the Secretary of the Company and with any Inspector of Elections at any meeting of the shareholders of the Company.

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      This proxy is irrevocable and shall survive the insolvency, incapacity, death or liquidation of the undersigned. Dated: August, 10 2004.

Signature

Name (and Title)

Shares of Company Common Stock
beneficially owned:

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