<PAGE>
                                                                     EXHIBIT 4.3



THIS WARRANT AND THE SHARES ISSUABLE HEREUNDER HAVE NOT BEEN REGISTERED UNDER
THE SECURITIES ACT OF 1933, AS AMENDED, AND MAY NOT BE SOLD, PLEDGED OR
OTHERWISE TRANSFERRED WITHOUT AN EFFECTIVE REGISTRATION THEREOF UNDER SUCH ACT
OR PURSUANT TO RULE 144 OR AN OPINION OF COUNSEL REASONABLY SATISFACTORY TO THE
CORPORATION AND ITS COUNSEL THAT SUCH REGISTRATION IS NOT REQUIRED.

                            WARRANT TO PURCHASE STOCK

Corporation:               WEBSIDESTORY, INC., a California Corporation
Number of Shares:          80,000
Class of Stock:            Common
Initial Exercise Price:    $2.50 per share
Issue Date:                March 27, 2000
Expiration Date:           March 26, 2005 (Subject to Article 4.1)

        THIS WARRANT CERTIFIES THAT, in consideration of the payment of $1.00
and for other good and valuable consideration, IMPERIAL BANCORP or registered
assignee ("Holder") is entitled to purchase the number of fully paid and
nonassessable shares of the class of securities (the "Shares") of the
corporation (the "Company") at the initial exercise price per Share (the
"Warrant Price") all as set forth above and as adjusted pursuant to Article 2 of
this Warrant, subject to the provisions and upon the terms and conditions set
forth of this Warrant.

ARTICLE 1. EXERCISE

        1.1 Method of Exercise. Holder may exercise this Warrant by delivering
this Warrant and a duly executed Notice of Exercise in substantially the form
attached as Appendix 1 to the principal office of the Company. Unless Holder is
exercising the conversion right set forth in Section 1.2, Holder shall also
deliver to the Company a check for the aggregate Warrant Price for the Shares
being purchased.

        1.2 Conversion Right. In lieu of exercising this Warrant as specified in
Section 1.1, Holder may from time to time convert this Warrant, in whole or in
part, into a number of Shares determined by dividing (a) the aggregate fair
market value of the Shares or other securities otherwise issuable upon exercise
of this Warrant minus the aggregate Warrant Price of such Shares by (b) the fair
market value of one Share. The fair market value of the Shares shall be
determined pursuant to Section 1.3.

        1.3 Fair Market Value. If the Shares are traded regularly in a public
market, the fair market value of the Shares shall be the closing price of the
Shares (or the closing price of the Company's stock into which the Shares are
convertible) reported for the business day immediately before Holder delivers
its Notice of Exercise to the Company. If the Shares are not regularly traded in
a public market, the Board of Directors of the Company shall determine fair
market value in its reasonable good faith judgment. The foregoing
notwithstanding, if Holder advises the Board of Directors in writing that Holder
disagrees with such determination,


                                       1
<PAGE>

then the Company and Holder shall promptly agree upon a reputable investment
banking firm to undertake such valuation. If the valuation of such investment
banking firm is greater than that determined by the Board of Directors, then all
fees and expenses of such investment banking firm shall be paid by the Company.
In all other circumstances, such fees and expenses shall be paid by Holder.

        1.4 Delivery of Certificate and New Warrant. Promptly after Holder
exercises or converts this Warrant, the Company shall deliver to Holder
certificates for the Shares acquired and, if this Warrant has not been fully
exercised or converted and has not expired, a new Warrant representing the
Shares not so acquired.

        1.5 Replacement of Warrants. On receipt of evidence reasonably
satisfactory to the Company of the loss, theft, destruction or mutilation of
this Warrant and, in the case of loss, theft or destruction, on delivery of an
indemnity agreement reasonably satisfactory in form and amount to the Company
or, in the case of mutilation, on surrender and cancellation of this Warrant,
the Company at its expense shall execute and deliver, in lieu of this Warrant, a
new warrant of like tenor.

        1.6 Repurchase on Sale, Merger, or Consolidation of the Company.

               1.6.1. Acquisition. For the purpose of this Warrant,
"Acquisition" means any sale, license, or other disposition of all or
substantially all of the assets (including intellectual property) of the
Company, or any reorganization, consolidation, or merger of the Company where
the holders of the Company's securities before the transaction beneficially own
less than 50% of the outstanding voting securities of the surviving entity after
the transaction.

               1.6.2. Assumption of Warrant. If upon the closing of any
Acquisition the successor entity assumes the obligations of this Warrant, then
this Warrant shall be exercisable for the same securities, cash, and property as
would be payable for the Shares issuable upon exercise of the unexercised
portion of this Warrant as if such Shares were outstanding on the record date
for the Acquisition and subsequent closing. The Warrant Price shall be adjusted
accordingly. The Company shall use reasonable efforts to cause the surviving
corporation to assume the obligations of this Warrant.

               1.6.3. Nonassumption. If upon the closing of any Acquisition the
successor entity does not assume the obligations of this Warrant and Holder has
not otherwise exercised this Warrant in full, then the unexercised portion of
this Warrant shall be deemed to have been automatically converted pursuant to
Section 1.2 and thereafter Holder shall participate in the Acquisition on the
same terms as other holders of the same class of securities of the Company.





ARTICLE 2. ADJUSTMENTS TO THE SHARES.


                                       2
<PAGE>

        2.1 Stock Dividends, Splits, Etc. If the Company declares or pays a
dividend on its common stock payable in common stock, or other securities,
subdivides the outstanding common stock into a greater amount of common stock,
then upon exercise of this Warrant, for each Share acquired, Holder shall
receive, without cost to Holder, the total number and kind of securities to
which Holder would have been entitled had Holder owned the Shares of record as
of the date the dividend or subdivision occurred.

        2.2 Reclassification, Exchange or Substitution. Upon any
reclassification, exchange, substitution, combination, or other event that
results in a change of the number and/or class of the securities issuable upon
exercise or conversion of this Warrant, Holder shall be entitled to receive,
upon exercise or conversion of this Warrant, the number and kind of securities
and property that Holder would have received for the Shares if this Warrant had
been exercised immediately before such reclassification, exchange, substitution,
or other event. Such an event shall include any automatic conversion of the
outstanding or issuable securities of the Company of the same class or series as
the Shares to common stock pursuant to the terms of the Company's Articles of
Incorporation upon the closing of a registered public offering of the Company's
common stock. The Company or its successor shall promptly issue to Holder a new
Warrant for such new securities or other property. The new Warrant shall provide
for adjustments which shall be as nearly equivalent as may be practicable to the
adjustments provided for in this Article 2 including, without limitation,
adjustments to the Warrant Price and to the number of securities or property
issuable upon exercise of the new Warrant. The provisions of this Section 2.2
shall similarly apply to successive reclassifications, exchanges, substitutions,
or other events.

        2.3 Adjustments for Combinations, Etc. If the outstanding Shares are
combined or consolidated, by reclassification or otherwise, into a lesser number
of shares, the Warrant Price shall be proportionately increased, and the number
of shares to which Holder is entitled to receive upon exercise or conversion of
this Warrant shall be adjusted accordingly.

        2.4 Adjustments for Diluting Issuances. The Warrant Price and the number
of Shares issuable upon exercise of this Warrant shall be subject to adjustment,
from time to time, in the manner set forth on Exhibit A, if attached, in the
event of Diluting Issuances (as defined on Exhibit A).

        2.5 No Impairment. The Company shall not, by amendment of its Articles
of Incorporation or through a reorganization, transfer of assets, consolidation,
merger, dissolution, issue, or sale of securities or any other voluntary action,
avoid or seek to avoid the observance or performance of any of the terms to be
observed or performed under this Warrant by the Company, but shall at all times
in good faith assist in carrying out all the provisions of this Article 2 and in
taking all such action as may be necessary or appropriate to protect Holder's
rights under this Article against impairment. If the Company takes any action
affecting the Shares or its common stock other than as described above that
adversely affects Holder's rights under this Warrant, the Warrant Price shall be
adjusted downward and the number of Shares issuable upon exercise of this
Warrant shall be adjusted upward in such a manner that the aggregate Warrant
Price of this Warrant is unchanged.


                                       3
<PAGE>

        2.6 Certificate as to Adjustments. Upon each adjustment of the Warrant
Price, the Company at its expense shall promptly compute such adjustment, and
furnish Holder with a certificate of its Chief Financial Officer setting forth
such adjustment and the facts upon which such adjustment is based. The Company
shall, upon written request, furnish Holder a certificate setting forth the
Warrant Price in effect upon the date thereof and the series of adjustments
leading to such Warrant Price.

ARTICLE 3. REPRESENTATIONS AND COVENANTS OF THE COMPANY.

        3.1 Representations and Warranties. The Company hereby represents and
warrants to the Holder as follows:

               (a) The initial Warrant Price referenced on the first page of
this Warrant is not greater than the fair market value of the Shares as of the
date of this Warrant.

               (b) All Shares which may be issued upon the exercise of the
purchase right represented by this Warrant, and all securities, if any, issuable
upon conversion of the Shares, shall, upon issuance, be duly authorized, validly
issued, fully paid and nonassessable, and free of any liens and encumbrances
except for restrictions on transfer provided for herein or under applicable
federal and state securities laws.

        3.2 Notice of Certain Events. If the Company proposes at any time (a) to
declare any dividend or distribution upon its common stock, whether in cash,
property, stock, or other securities and whether or not a regular cash dividend;
(b) to offer for subscription pro rata to the holders of any class or series of
its stock any additional shares of stock of any class or series or other rights;
(c) to effect any reclassification or recapitalization of common stock; (d) to
merge or consolidate with or into any other corporation, or sell, lease,
license, or convey all or substantially all of its assets, or to liquidate,
dissolve or wind up; or (e) offer holders of registration rights the opportunity
to participate in an underwritten public offering of the company's securities
for cash, then, in connection with each such event, the Company shall give
Holder (1) at least 20 days prior written notice of the date on which a record
will be taken for such dividend, distribution, or subscription rights (and
specifying the date on which the holders of common stock will be entitled
thereto) or for determining rights to vote, if any, in respect of the matters
referred to in (c) and (d) above; (2) in the case of the matters referred to in
(c) and (d) above at least 20 days prior written notice of the date when the
same will take place (and specifying the date on which the holders of common
stock will be entitled to exchange their common stock for securities or other
property deliverable upon the occurrence of such event); and (3) in the case of
the matter referred to in (e) above, the same notice as is given to the holders
of such registration rights.

        3.3 Information Rights. So long as the Holder holds this Warrant and/or
any of the Shares, the Company shall deliver to the Holder (a) promptly after
mailing, copies of all communiques to the shareholders of the Company, (b)
within ninety (90) days after the end of each fiscal year of the Company, the
annual audited financial statements of the Company certified by independent
public accountants of recognized standing and (c) within forty-five (45)


                                       4
<PAGE>

days after the end of each of the first three quarters of each fiscal year, the
Company's quarterly, unaudited financial statements.

        3.4 Registration Under Securities Act of 1933, as amended. The Company
agrees that the Shares shall be subject to the registration rights set forth on
Exhibit B.

ARTICLE 4. MISCELLANEOUS.

        4.1 Term: Notice of Expiration. This Warrant is exercisable, in whole or
in part, at any time and from time to time on or before the Expiration Date set
forth above. The Company shall give Holder written notice of Holder's right to
exercise this Warrant in the form attached as Appendix 2 not more than 90 days
and not less than 30 days before the Expiration Date. If the notice is not so
given, the Expiration Date shall automatically be extended until 30 days after
the date the Company delivers the notice to Holder.

        4.2 Legends. This Warrant and the Shares (and the securities issuable,
directly or indirectly, upon conversion of the Shares, if any) shall be
imprinted with a legend in substantially the following form:

        THIS SECURITY HAS NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933,
        AS AMENDED, AND MAY NOT BE SOLD, PLEDGED OR OTHERWISE TRANSFERRED
        WITHOUT AN EFFECTIVE REGISTRATION THEREOF UNDER SUCH ACT OR PURSUANT TO
        RULE 144 OR AN OPINION OF COUNSEL REASONABLY SATISFACTORY TO THE
        CORPORATION AND ITS COUNSEL THAT SUCH REGISTRATION IS NOT REQUIRED.

        4.3 Compliance with Securities Laws on Transfer. This Warrant and the
Shares issuable upon exercise this Warrant (and the securities issuable,
directly or indirectly, upon conversion of the Shares, if any) may not be
transferred or assigned in whole or in part without compliance with applicable
federal and state securities laws by the transferor and the transferee
(including, without limitation, the delivery of investment representation
letters and legal opinions reasonably satisfactory to the Company). The Company
shall not require Holder to provide an opinion of counsel if the transfer is to
an affiliate of Holder or if there is no material question as to the
availability of current information as referenced in Rule 144(c), Holder
represents that it has complied with Rule 144(d) and (e) in reasonable detail,
the selling broker represents that it has complied with Rule 144(f), and the
Company is provided with a copy of Holder's notice of proposed sale.

        4.4 Transfer Procedure. Subject to the provisions of Section 4.3, Holder
may transfer all or part of this Warrant or the Shares issuable upon exercise of
this Warrant (or the securities issuable, directly or indirectly, upon
conversion of the Shares, if any) by giving the Company notice of the portion of
the Warrant being transferred setting forth the name, address and taxpayer
identification number of the transferee and surrendering this Warrant to the
Company for reissuance to the transferee(s) (and Holder, if applicable). Unless
the Company is filing financial information with the SEC pursuant to the
Securities Exchange Act of 1934, the


                                       5
<PAGE>

Company shall have the right to refuse to transfer any portion of this Warrant
to any person who directly competes with the Company.

        4.5 Notices. All notices and other communications from the Company to
the Holder, or vice versa, shall be deemed delivered and effective when given
personally or mailed by first-class registered or certified mail, postage
prepaid, at such address as may have been furnished to the Company or the
Holder, as the case may be, in writing by the Company or such Holder from time
to time.

        4.6 Waiver. This Warrant and any term hereof may be changed, waived,
discharged or terminated only by an instrument in writing signed by the party
against which enforcement of such change, waiver, discharge or termination is
sought.

        4.7 Attorneys' Fees. In the event of any dispute between the parties
concerning the terms and provisions of this Warrant, the party prevailing in
such dispute shall be entitled to collect from the other party all costs
incurred in such dispute, including reasonable attorneys' fees.

        4.8 Governing Law. This Warrant shall be governed by and construed in
accordance with the laws of the State of California, without giving effect to
its principles regarding conflicts of law.


                                            WEBSIDESTORY, INC.


                                            By: /s/ JOHN HENTRICH
                                               ---------------------------------

                                            Name:   John Hentrich
                                                 -------------------------------

                                            Title:  President/CEO
                                                  ------------------------------

                                            By: /s/ MICHAEL CHRISTIAN
                                               ---------------------------------

                                            Name:   Michael Christian
                                                 -------------------------------

                                            Title:  SVP
                                                  ------------------------------


                                       6
<PAGE>

                                   APPENDIX 1

                               NOTICE OF EXERCISE


        1. The undersigned hereby elects to purchase __________ shares of the
Common Stock of WEBSIDESTORY, INC. pursuant to the terms of the attached
Warrant, and tenders herewith payment of the purchase price of such shares in
full.

        2. Please issue a certificate or certificates representing said shares
in the name of the undersigned or in such other name as is specified below:

                      Chief Financial Officer
                      Controllers Department
                      Imperial Bancorp
                      P.O. Box 92991
                      Los Angeles, CA 90009
                      Or Registered Assignee

        3. The undersigned represents it is acquiring the shares solely for its
own account and not as a nominee for any other party and not with a view toward
the resale or distribution thereof except in compliance with applicable
securities laws.

IMPERIAL BANCORP  or Registered Assignee



-----------------------------------
(Signature)


-------------------
(Date)


                                       7
<PAGE>

                                   APPENDIX 2

                     NOTICE THAT WARRANT IS ABOUT TO EXPIRE


                          _________________, __________


Chief Financial Officer
Controllers Department
Imperial Bancorp
P.O. Box 92991
Los Angeles, CA 90009
Or Registered Assignee

Gentleperson:

        This is to advise you that the Warrant issued to you described below
will expire on March 26, 2005.

Issuer:                                     WEBSIDESTORY, INC.

Issue Date:                                 March 27, 2000

Class of Security Issuable:                 Common

Exercise Price Per Share:                   $2.50

Number of Shares Issuable:                  80,000

Procedure for Exercise:

        Please contact [name of contact person at (phone number)] with any
questions you may have concerning exercise of the Warrant. This is your only
notice of pending expiration.

        WEBSIDESTORY, INC.

        By:
           -----------------------------

        Its:
            ----------------------------


                                       8
<PAGE>

                                    EXHIBIT B

                               Registration Rights


        The Shares shall be deemed "registrable securities" or otherwise
entitled to "piggy back" registration rights in accordance with the terms of the
following agreement (the "Agreement") between the Company and its investor(s):



               Reg. Rights AGMT. June 18, 1999
               ----------------------------------------------------------------
               [Identify Agreement by date, title and parties.  If no Agreement
               exists, indicate by "none."]

        The Company agrees that no amendments will be made to the Agreement
which would have an adverse impact on Holder's registration thereunder without
the consent of Holder. By acceptance of the Warrant to which this Exhibit B is
attached, Holder shall not be deemed to be a party to the Agreement, but solely
entitled to the registration rights created thereby.

        If no Agreement exists, then the Company and the Holder shall enter into
Holder's standard form of Registration Rights Agreement as in effect on the
Issue Date of the Warrant.





                                       9
<PAGE>

                              AMENDMENT TO WARRANT

      This Amendment to Warrant is entered into on August 21th, 2000, by and
between WEBSIDESTORY, INC. ("Company") and IMPERIAL BANCORP, ("Holder").

      Holder was issued a warrant dated March 27, 2000 by Company (the
"Warrant") and in connection with an additional extension of credit by Imperial
Bank, Company agreed to amend the Initial Exercise Price of the Shares specified
therein.

      In consideration of the additional extension of credit and the provisions
hereof, it is agreed as follows:

      1. The Initial Exercise Price is hereby amended to be $1.35.

      2. Except as amended hereby, the terms and provisions of the are ratified
and confirmed and are in full force and effect.

      This Amendment is executed by duly authorized persons as of the date first
above written.

                                  WEBSIDESTORY, INC.

                                  By: /s/ [ILLEGIBLE]
                                     -------------------------------------------
                                  Title: SRVP CFO

                                  By: /s/ John Hentrich
                                     -------------------------------------------
                                  Title: CEO

                                  IMPERIAL BANCORP

                                  By: /s/ [ILLEGIBLE]
                                  Title:VP

                                  By: __________________________________________
                                  Title: _______________________________________