Document:

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                                                                     EXHIBIT 4.1

COMMON STOCK                                                      COMMON STOCK
WSSI NUMBER                                                          SHARES

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

INCORPORATED UNDER THE                                 SEE REVERSE FOR CERTAIN
  LAWS OF DELAWARE                                  DEFINITIONS AND RESTRICTIONS

                               WebSideStory, Inc.
                                                              CUSIP

THIS CERTIFIES THAT:

IS THE HOLDER OF

             FULLY PAID AND NON-ASSESSABLE SHARES OF COMMON STOCK,
                         $0.001 PAR VALUE PER SHARE, OF

                               WEBSIDESTORY, INC.
         -------------------------------------------------------------

transferable on the books of the Corporation by the holder hereof in person or
by duly authorized attorney upon surrender of this Certificate properly
endorsed. This Certificate is not valid until countersigned by the Transfer
Agent and registered by the Registrar.

     WITNESS the facsimile seal of the Corporation and the facsimile signatures
of its duly authorized officers.

Dated:

/s/ Michael S. Christian                                 /s/ Jeffrey W. Lunsford
------------------------                                 -----------------------
SECRETARY                       [CORPORATE SEAL]         CHIEF EXECUTIVE OFFICER

COUNTERSIGNED AND REGISTERED
                      U.S. STOCK TRANSFER CORPORATION    TRANSFER AGENT
                                                         AND REGISTRAR

                                                         AUTHORIZED SIGNATURE

                                     [LOGO]

     A statement of the powers, designations, preferences and relative,
participating, optional or other special rights of each class of stock or series

<PAGE>

thereof and the qualifications, limitations or restrictions of such preferences
and/or rights as established, from time to time, by the Certificate of
Incorporation of the Corporation and by any certificate of determination, and
the number of shares constituting each class and series and the designations
thereof, may be obtained by the holder hereof upon written request and without
charge from the Secretary of the Corporation at the principal office of the
Corporation.

     The following abbreviations, when used in the inscription on the face of
this certificate, shall be construed as though they were written out in full
according to applicable laws or regulations:

     TEN COM-  as tenants in common
     TEN ENT-  as tenants by the entireties
      JT TEN-  as joint tenants with
               right of survivorship and
               not as tenants in common

UNIF GIFT MIN ACT-                       CUSTODIAN
                   ---------------------           --------------------------
                          (CUST)                              (MINOR)

                         under Uniform Gifts to Minors

                         Act
                             ------------------------------------------------
                                                  (State)

UNIF TRF MIN ACT-                        Custodian (until age      )
                  ----------------------                      ----
                         (Cust)

                                 under Uniform Transfer to Minors Act
                  -------------                                       ----------
                     (Minor)                                            (State)

Additional abbreviations may also be used though not in the above list.

FOR VALUE RECEIVED,                     hereby sell, assign and transfer unto
                    -------------------

PLEASE INSERT SOCIAL SECURITY OR OTHER
IDENTIFY NUMBER OF ASSIGNEE

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

-------------------------------------------------------------------------------
(PLEASE PRINT OR TYPEWRITE NAME AND ADDRESS, INCLUDING ZIP CODE, OF ASSIGNEE)

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

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

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

---------------------------------------------------------------------- Shares
of the common stock represented by the within Certificate, and do(es) hereby
irrevocably constitute and appoint
                                   ------------------------------------------
Attorney to transfer the said stock on the books of the within named
Corporation with full power of substitution in the premises.

Dated:                                  x
      -------------------------------     --------------------------------------

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                                 X_____________________________________________
                                  NOTICE: THE SIGNATURE(S) TO THE ASSIGNMENT
                                  MUST CORRESPOND WITH THE NAME(S) AS WRITTEN
                                  UPON THE FACE OF THE CERTIFICATE IN EVERY
                                  PARTICULAR, WITHOUT ALTERATION OR ENLARGEMENT
                                  OR ANY CHANGE WHATSOEVER.

Signature(s) Guaranteed:    By ________________________________________________
                               THE SIGNATURE(S) SHOULD BE GUARANTEED BY AN
                               ELIGIBLE GUARANTOR INSTITUTION (BANKS,
                               STOCKBROKERS, SAVINGS AND LOAN ASSOCIATIONS AND
                               CREDIT UNIONS WITH MEMBERSHIP IN AN APPROVED
                               SIGNATURE GUARANTEE MEDALLION PROGRAM), PURSUANT
                               TO S.E.C. RULE 17Ad-15.

     Keep this certificate in a safe place. If it is lost, stolen, or destroyed
the Corporation will require a bond of indemnity as a condition to the issuance
of a replacement certificate.<PAGE>
                                                                     EXHIBIT 4.8

                               WEBSIDESTORY, INC.

                   AMENDMENT TO REGISTRATION RIGHTS AGREEMENT

      This Amendment (the "AMENDMENT") dated as of July 21, 2004 is entered into
by and among WebSideStory, Inc., a Delaware corporation (the "COMPANY"), Blaise
P. Barrelet ("BARRELET") and certain investors as listed on Schedule A attached
hereto (the "INVESTORS").

                                    RECITALS

      WHEREAS, the Company and the Investors entered into that certain
Registration Rights Agreement dated June 18, 1999, as amended on June 30, 2000,
December 12, 2000 and March 2, 2001 (collectively, the "ORIGINAL AGREEMENT"),
under which the Company granted certain registration rights to the Investors;

      WHEREAS, the Company has filed a Registration Statement on Form S-1 for
its initial public offering (the "REGISTRATION STATEMENT") in which the Company
intends to sell shares of its common stock (the "COMMON STOCK");

      WHEREAS, pursuant to the Original Agreement, the Investors' right to sell
shares of Common Stock pursuant to the Registration Statement is senior to the
ability of Barrelet to sell shares of Common Stock pursuant to the Registration
Statement;

      WHEREAS, upon the occurrence of certain events, the Company and the
Investors desire to include a portion of Barrelet's Common Stock in the
Registration Statement by amending the Original Agreement;

      WHEREAS, the Original Agreement provides that an amendment of the Original
Agreement may be effected by the written consent of the Company and a Majority
Interest (as such term is defined in the Original Agreement) of the Investors;
and

      WHEREAS, the undersigned Investors constitute holders of not less than a
Majority Interest of the Investors and, therefore, are entitled to bind all
other holders of Registrable Securities (as such term is defined in the Original
Agreement) who are parties to the Original Agreement.

                                    AGREEMENT

      NOW, THEREFORE, in consideration of the mutual covenants and agreements
set forth herein and for other good and valuable consideration, the receipt and
adequacy of which are hereby acknowledged, the parties hereby agree as follows:
<PAGE>
      1. Piggyback Registration. Section 4 is hereby amended in its entirety to
read as follows:

            "4. Piggyback Registration.

                  (a) If the Company at any time proposes to register any of its
            Common Stock under the Securities Act for sale to the public
            (including pursuant to a demand under Section 2 hereof as provided
            therein and except with respect to registration statements on Forms
            S-4, S-8 or another form not available for registering the
            Registrable Securities for sale to the public), each such time it
            will give written notice at the applicable address of record to each
            holder of Registrable Securities of its intention to do so. Upon the
            written request of any of such holders of the Registrable
            Securities, given within thirty (30) days after receipt by such
            Person of such notice, the Company will, subject to the limits
            contained in this Section 4, use its reasonable best efforts to
            cause all such Registrable Securities of said requesting holders to
            be registered under the Securities Act and qualified for sale under
            any state blue sky law, all to the extent required to permit such
            sale or other disposition of said Registrable Securities; provided,
            however, that if the Company is advised in writing in good faith by
            any managing underwriter of the Company's securities being offered
            in a public offering pursuant to such registration statement that
            the amount to be sold by persons other than the Company
            (collectively, "Selling Stockholders") is greater than the amount
            which can be offered without adversely affecting the offering, the
            Company may reduce the amount offered for the accounts of Selling
            Stockholders (including such holders of shares of Registrable
            Securities) to a number deemed satisfactory by such managing
            underwriter; and provided further, that the shares to be excluded
            shall be determined in the following sequence (except with respect
            to a demand under Section 2 hereof): (i) first, securities held by
            any Persons not having any such contractual, incidental registration
            rights; (ii) second, securities held by any Persons having
            contractual, incidental registration rights pursuant to an agreement
            which is not this Agreement; (iii) third, securities held by the
            Founders (as defined in the Purchase Agreement); and (iv) fourth,
            all Registrable Securities in each case as determined on a pro rata
            basis in accordance with their holdings. Notwithstanding the
            foregoing, except with respect to the Company's first registration
            of Common Stock pursuant to the Securities Act, in no event shall
            the number of Registrable Securities included in a registration
            pursuant to this section be reduced to less than twenty percent
            (20%) of all shares to be registered.

                                       2
<PAGE>
            (b) Notwithstanding Section 4(a), with respect to the Registration
            Statement previously filed in connection with the Company's initial
            public offering (and only with respect to such Registration
            Statement), this Section 4(b) shall govern. Neither the Investors
            nor Barrelet shall have any right to sell securities pursuant to the
            Registration Statement or in connection with the Company's initial
            public offering except as follows. In addition, the Investors hereby
            waive any right to notice of the filing of the Registration
            Statement.

                  (i) The Investors shall be entitled to sell such number of
            shares of Registrable Securities pursuant to the Registration
            Statement as is equal to 12% of the total number of securities to be
            sold (excluding the over-allotment option).

                  (ii) (A) In the event that the value of the Company
            immediately prior to the effectiveness of the Registration Statement
            is less than $150,000,000, as determined by multiplying the proposed
            public offering price per share by the number of outstanding shares
            of Common Stock of the Company immediately prior to the
            effectiveness of the Registration Statement (assuming exercise or
            conversion of all outstanding securities exercisable for or
            convertible into the Company's Common Stock), then the Investors
            shall be entitled to include such number of shares of Registrable
            Securities in the over-allotment option contemplated by the
            Registration Statement as is equal to 50% of the total number of
            securities to be sold, if any, in such over-allotment option; and

                       (B) In the event that the value of the Company
            immediately prior to the effectiveness of the Registration Statement
            is equal to or greater than $150,000,000, as determined by
            multiplying the proposed initial public offering price per share by
            the number of outstanding shares of Common Stock of the Company
            immediately prior to the effectiveness of the Registration Statement
            (assuming exercise or conversion of all outstanding securities
            exercisble for or convertible into the Company's Common Stock), then
            the Investors shall be entitled to include such number of shares of
            Registrable Securities in the over-allotment option contemplated by
            the Registration Statement as is equal to 40% of the total number of
            securities to be sold, if any, in such over-allotment option and
            Barrelet shall be entitled to include such number of shares of
            Common Stock held by him in the over-allotment option contemplated
            by the Registration Statement as is equal to 20% of the total number
            of securities to be sold, if any, in such over-allotment option and
            such shares of Common Stock held

                                       3
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            by Barrelet shall be deemed "Registrable Securities" under the
            Original Agreement with respect to such sale."

       2. Effectiveness of Amendment. In accordance with Section 9 of the
Original agreement, this Amendment will not be effective unless and until the
Company and a Majority in Interest of the Investors consent in writing to this
Amendment.

      3. No other waivers; modifications. Except as otherwise expressly provided
in this Amendment, no other portion, section or provision of the Original
Agreement is waived or amended and the Original Agreement shall continue in full
force and effect, in accordance with its terms.

      4. Miscellaneous. This Amendment will be governed in all respects by the
laws of the State of California. This Amendment and the Original Agreement
constitute the full and entire understanding and agreement among the parties
with regard to the subjects hereof and supersede all prior written and oral
agreements, representations and commitments, if any, among the parties with
respect to such subjects. This Amendment may be executed in any number of
counterparts, each of which will be an original, but all of which together will
constitute one instrument. Any provision of this Amendment may be waived or
amended only in accordance with the provisions set forth in the Original
Agreement.

             [The remainder of this page intentionally left blank.]

                                       4
<PAGE>

      IN WITNESS WHEREOF, the parties hereto have executed this Amendment on the
date first set forth above.

                                          "COMPANY"

                                          WEBSIDESTORY, INC.

                                          /s/ Jeffrey W. Lunsford
                                          -----------------------
                                          Jeffrey W. Lunsford
                                          President and Chief Executive Officer

         [SIGNATURE PAGE TO AMENDMENT TO REGISTRATION RIGHTS AGREEMENT]
<PAGE>

         IN WITNESS WHEREOF, the parties hereto have executed this Amendment on
the date first set forth above.

                                        "BARRELET"

                                        /s/ Stuart Hurwitz

                                        -----------------------
                                        Stuart Hurwitz, as Attorney-in-Fact for
                                        Blaise P. Barrelet

         [SIGNATURE PAGE TO AMENDMENT TO REGISTRATION RIGHTS AGREEMENT]
<PAGE>
      IN WITNESS WHEREOF, the parties hereto have executed this Amendment on the
date first set forth above.

                                   "INVESTORS"

                                   TA/ADVENT VIII L.P.
                                   By: TA Associates VIII LLC, its
                                       General Partner
                                   By: TA Associates, Inc., its Manager

                                                *
                                   By:_______________________

                                   ADVENT ATLANTIC AND PACIFIC III L.P.
                                   By: TA Associates AAP III Partners,
                                       its General Partner

                                   By: TA Associates, Inc., its General Partner

                                                *
                                   By:_______________________

                                   TA INVESTORS LLC
                                   By: TA Associates, Inc., its Manager
                                                *
*By: /s/ Kurt R. Jaggers           By:________________________
    --------------------
         Kurt R. Jaggers
         Managing Director

                                   TA EXECUTIVES FUND LLC
                                   By: TA Associates, Inc., its Manager
                                                *
                                   By:_________________________

         [SIGNATURE PAGE TO AMENDMENT TO REGISTRATION RIGHTS AGREEMENT]
<PAGE>
         IN WITNESS WHEREOF, the parties hereto have executed this Amendment on
the date first set forth above.

                                   "INVESTORS"

                                   SUMMIT INVESTORS III, L.P.
                                                *
                                   By:_______________________
                                   General Partner

                                   SUMMIT V ADVISORS FUND (QP), L.P.
                                   By: Summit Partners V, L.P., its
                                       General Partner
                                   By: Summit Partners, LLC, its General Partner

                                                *
                                   By:_______________________

                                   SUMMIT V ADVISORS FUND, L.P.
                                   By: Summit Partners V, L.P., its
                                       General Partner
                                   By: Summit Partners, LLC, its General Partner

                                                *
*By: /s/ Walter G. Kortschak       By:________________________
     -----------------------
         Walter G. Kortschak
         Managing Director

                                   SUMMIT V COMPANION FUND, L.P.
                                   By: Summit Partners V, L.P., its
                                       General Partner
                                   By: Summit Partners, LLC, its General Partner

                                                *
                                   By:_________________________

                                   SUMMIT VENTURES V, L.P.
                                   By: Summit Partners V, L.P., its
                                       General Partner
                                   By: Summit Partners, LLC, its General Partner

                                                *
                                   By:_________________________

         [SIGNATURE PAGE TO AMENDMENT TO REGISTRATION RIGHTS AGREEMENT]
<PAGE>
         IN WITNESS WHEREOF, the parties hereto have executed this Amendment on
the date first set forth above.

                                        "INVESTORS"

                                        WESTCLIFF PARTNERS, LP.
                                        By:  Westcliff Capital Management, LLC,
                                             its General Partner
                                                     *
                                        By:________________________

                                        WESTCLIFF AGGRESSIVE GROWTH, LP.
                                        By:  Westcliff Capital Management, LLC,
                                             its General Partner
                                                     *
                                        By:________________________

                                        WESTCLIFF LONG/SHORT, LP.
                                        By:  Westcliff Capital Management, LLC,
                                             its General Partner
                                                     *
*By ______________________              By:________________________
      Richard Spencer
      General Partner                   WESTCLIFF MASTER FUND, LP.
                                        By:  Westcliff Capital Management, LLC,
                                             its General Partner
                                                     *
                                        By:________________________

                                        PALM TRUST
                                        By:  Westcliff Capital Management, LLC,
                                             its Investment Advisor
                                                     *
                                        By:________________________

                                        WESTCLIFF PROFIT SHARING PLAN
                                        By:  Westcliff Capital Management, LLC,
                                             its General Partner
                                                     *
                                        By:________________________

                                        WESTCLIFF SMALL CAP FUND, LP.
                                        By:  Westcliff Capital Management, LLC,
                                             its General Partner
                                                     *
                                        By:________________________

         [SIGNATURE PAGE TO AMENDMENT TO REGISTRATION RIGHTS AGREEMENT]
<PAGE>
      IN WITNESS WHEREOF, the parties hereto have executed this Amendment on the
date first set forth above.

                                        "INVESTORS"

                                        PENINSULA FUND L.P.

                                        By:_______________________
                                        Scott Bedford
                                        President

         [SIGNATURE PAGE TO AMENDMENT TO REGISTRATION RIGHTS AGREEMENT]
<PAGE>
      IN WITNESS WHEREOF, the parties hereto have executed this Amendment on the
date first set forth above.

                                        "INVESTORS"

                                        -----------------------
                                        John Hentrich

         [SIGNATURE PAGE TO AMENDMENT TO REGISTRATION RIGHTS AGREEMENT]
<PAGE>
         IN WITNESS WHEREOF, the parties hereto have executed this Amendment on
the date first set forth above.

                                        "INVESTORS"

                                        -----------------------
                                        Keith Fisher

         [SIGNATURE PAGE TO AMENDMENT TO REGISTRATION RIGHTS AGREEMENT]
<PAGE>

                                   SCHEDULE A

                                    INVESTORS

JOHN HENTRICH
KEITH FISHER
TA/ADVENT VIII L.P.
ADVENT ATLANTIC AND PACIFIC III L.P.
TA INVESTORS LLC
TA EXECUTIVES FUND LLC
SUMMIT INVESTORS III, L.P.
SUMMIT V ADVISORS FUND (QP), L.P.
SUMMIT V ADVISORS FUND, L.P.
SUMMIT V COMPANION FUND, L.P.
SUMMIT VENTURES V, L.P.
WESTCLIFF PARTNERS, LP.
WESTCLIFF AGGRESSIVE GROWTH, LP.
WESTCLIFF LONG/SHORT, LP.
WESTCLIFF MASTER FUND, LP.
PALM TRUST
WESTCLIFF PROFIT SHARING PLAN
WESTCLIFF SMALL CAP FUND, LP.
PENINSULA FUND L.P.

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