<PAGE>   1
                                                                   EXHIBIT 10.15



                                  WEBSIDESTORY

                PROPRIETARY INFORMATION AND INVENTIONS AGREEMENT

In consideration of my employment or continued employment by WEBSIDESTORY (the
"Company"), and the compensation now and hereafter paid to me, I, JOHN HENTRICH,
hereby agree as follows:



1.    NONDISCLOSURE

1.1   RECOGNITION OF COMPANY'S RIGHTS; NONDISCLOSURE. At all times during my
employment and thereafter, I will hold in strictest confidence and will not
disclose, use, lecture upon or publish any of the Company's Proprietary
Information (defined below), except as such disclosure, use or publication may
be required in connection with my work for the Company, or unless an officer of
the Company expressly authorizes such in writing. I will obtain Company's
written approval before publishing or submitting for publication any material
(written, verbal, or otherwise) that relates to my work at Company and/or
incorporates any Proprietary Information. I hereby assign to the Company any
rights I may have or acquire in such Proprietary Information and recognize that
all Proprietary Information shall be the sole property of the Company and its
assigns.

1.2   PROPRIETARY INFORMATION. The term "Proprietary Information" shall mean any
and all confidential and/or proprietary knowledge, data or information of the
Company. By way of illustration but not limitation, "Proprietary Information"
includes tangible and intangible information relating to antibodies and other
biological materials, cell lines, samples of assay components, media and/or cell
lines and procedures and formulations for producing any such assay components,
media and/or cell lines, formulations, products, processes, know-how, designs,
formulas, methods, developmental or experimental work, clinical data,
improvements, discoveries, plans for research, new products, marketing and
selling, business plans, budgets and unpublished financial statements, licenses,
prices and costs, suppliers and customers, and information regarding the skills
and compensation of other employees of the Company.

1.3   THIRD PARTY INFORMATION. I understand, in addition, that the Company has
received and in the future will receive from third parties confidential or
proprietary information ("Third Party Information") subject to a duty on the
Company's part to maintain the confidentiality of such information and to use it
only for certain limited purposes. During the term of my employment and
thereafter, I will hold Third Party Information in the strictest confidence and
will not disclose to anyone (other than Company personnel who need to know such
information in connection with their work for the Company) or use, except in
connection with my work for the Company, Third Party Information unless
expressly authorized by an officer of the Company in writing.

1.4   NO IMPROPER USE OF INFORMATION OF PRIOR EMPLOYERS AND OTHERS. During my
employment by the Company I will not improperly use or disclose any confidential
information or trade secrets, if any, of any former employer or any other person
to whom I have an obligation of confidentiality, and I will not bring, onto the
premises of the Company any unpublished documents or any property belonging to
any former employer or any other person to whom I have an obligation of
confidentiality unless consented to in writing by that former employer or
person. I will use in the performance of my duties only information which is
generally known and used by persons with training and experience comparable to
my own, which is common knowledge in the industry or otherwise legally in the
public domain, or which is otherwise provided or developed by the Company.

2.    ASSIGNMENT OF INVENTIONS.

2.1   PROPRIETARY RIGHTS. The term "Proprietary Rights" shall mean all trade
secret, patent, copyright, mask work and other intellectual property rights
throughout the world.

2.2   PRIOR INVENTIONS. Inventions, if any, patented or unpatented, which I made
prior to the commencement of my employment with the Company are excluded from
the scope of this Agreement. To preclude any possible uncertainty, I have set
forth on Exhibit-2 (Previous Inventions) attached hereto a complete list of all
Inventions that I have, alone or jointly with others, conceived, developed or
reduced to practice or caused to be conceived, developed or reduced to practice
prior to the commencement of my employment with the Company, that I consider to
be my property or the property of third parties and that I wish to have excluded
from the scope of this Agreement (collectively referred to as "Prior
Inventions"). If disclosure of any such Prior Invention would cause me to
violate any prior confidentiality agreement, I understand that I am not to list
such Prior



                                       1.
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Inventions in Exhibit -2 but am only to disclose a cursory name for each such
invention, a listing of the party(ies) to whom it belongs and the fact that full
disclosure as to such inventions has not been made for that reason. A space is
provided on Exhibit -2 for such purpose. If no Such disclosure is attached, I
represent that there are no Prior Inventions. If, in the course of my employment
with the Company, I incorporate a Prior Invention into a Company product,
process or machine, the Company is hereby granted and shall have a nonexclusive,
royalty-free, irrevocable, perpetual, worldwide license (with rights to
sublicense through multiple tiers of sublicensees) to make, have made, modify,
use and sell such Prior Invention. Notwithstanding the foregoing, I agree that I
will not incorporate, or permit to be incorporated, Prior Inventions in any
Company Inventions without the Company's prior written consent.

2.3   ASSIGNMENT OF INVENTIONS. Subject to Sections 2.4 and 2.6, I hereby assign
and agree to assign in the future (when any such Inventions or Proprietary
Rights are first reduced to practice or first fixed in a tangible medium, as
applicable) to the Company all my right, title and interest in and to any and
all Inventions (and all Proprietary Rights with respect thereto) whether or not
patentable or registrable under copyright or similar statutes, made or conceived
or reduced to practice or learned by me, either alone or jointly with others,
during the period of my employment with the Company. Inventions assigned to the
Company, or to a third party as directed by the Company pursuant to this Section
2, are hereinafter referred to as "Company Inventions".

2.4   NONASSIGNABLE INVENTIONS. This Agreement does not apply to an Invention
which qualifies fully as a nonassignable Invention under Section 2870 of the
California Labor Code (hereinafter "Section 2870"). I have reviewed the
notification on Exhibit-1 (Limited Exclusion Notification) and agree that my
signature acknowledges receipt of the notification.

2.5   OBLIGATION TO KEEP COMPANY INFORMED. During the period of my employment
and for six (6) months after termination of my employment with the Company, I
will promptly disclose to the Company fully and in writing all Inventions
authored, conceived or reduced to practice by me, either alone or jointly with
others. In addition, I will promptly disclose to the Company all patent
applications filed by me or on my behalf within a year after termination of
employment. At the time of each such disclosure, I will advise the Company in
writing of any Inventions that I believe fully qualify for protection under
Section 2870; and I will at that time provide to the Company in writing, all
evidence necessary to substantiate that belief. The Company will keep in
confidence and will not use for any purpose or disclose to third parties without
my consent any confidential information disclosed in writing to the Company
pursuant to this Agreement relating to Inventions that qualify fully for
protection under the provisions of Section 2870. I will preserve the
confidentiality of any Invention that does not fully qualify for protection
under Section 2870.

2.6   GOVERNMENT OR THIRD PARTY. I also agree to assign all my right, title and
interest in and to any particular Company Invention to a third party, including
without limitation the United States, as directed by the Company.

2.7   WORKS FOR HIRE. I acknowledge that all original works of authorship which
are made by me (solely or jointly with others) within the scope of my employment
and which are protectable by copyright are "works made for hire", pursuant to
United States Copyright Act (17 U.S.C., Section 101).

2.8   ENFORCEMENT OF PROPRIETARY RIGHTS. I will assist the Company in every
proper way to obtain, and from time to time enforce, United States and foreign
Proprietary Rights relating to Company Inventions in any and all countries. To
that end I will execute, verify and deliver such documents and perform such
other acts (including appearances as a witness) as the Company may reasonably
request for use in applying for, obtaining, perfecting, evidencing, sustaining
and enforcing such Proprietary Rights and the assignment thereof. In addition, I
will execute, verify and deliver assignments of such Proprietary Rights to the
Company or its designee. My obligation to assist the Company with respect to
Proprietary Rights relating to such Company Inventions in any and all countries
shall continue beyond the termination of my employment, but the Company shall
compensate me at a reasonable rate after my termination for the time actually
spent by me at the Company's request on such assistance.

In the event the Company is unable for any reason, after reasonable effort, to
secure my signature on any document needed in connection with the actions
specified in the preceding paragraph, I hereby irrevocably designate and appoint
the Company and its duly authorized officers and agents as my agent and attorney
in fact, which appointment is coupled with an interest, to act for and in my
behalf to execute, verify and file any such documents and to do all other
lawfully permitted acts to further the purposes of the preceding paragraph with
the same legal force and



                                       2.
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effect as if executed by me. I hereby waive and quitclaim to the Company any and
all claims, of any nature whatsoever, which I now or may hereafter have for
infringement of any Proprietary Rights assigned hereunder to the Company.

3.    RECORDS. I agree to keep and maintain adequate and current records (in the
form of notes, sketches, drawings and in any other form that may be required by
the Company) of all Proprietary Information developed by me and all Inventions
made by me during the period of my employment at the Company, which records
shall be available to and remain the sole property of the Company at all times.

4.    ADDITIONAL ACTIVITIES. I agree that during the period of my employment by
the Company I will not, without the Company's express written consent, engage in
any employment or business activity which is competitive with, or would
otherwise conflict with, my employment by the Company. I agree further that for
the period of my employment by the Company and for one (1) year after the date
of termination of my employment by the Company I will not induce any employee of
the Company to leave the employ of the Company.

5.    NO CONFLICTING OBLIGATION. I represent that my performance of all the
terms of this Agreement and as an employee of the Company does not and will not
breach any agreement to keep in confidence information acquired by me in
confidence or in trust prior to my employment by the Company. I have not entered
into, and I agree I will not enter into, any agreement either written or oral in
conflict herewith.

6.    RETURN OF COMPANY DOCUMENTS. When I leave the employ of the Company, I
will deliver to the Company any and all drawings, notes, memoranda,
specifications, devices, formulas, and documents, together with all copies
thereof, and any other material containing or disclosing any Company Inventions,
Third Party Information or Proprietary Information of the Company. I further
agree that any property situated on the Company's premises and owned by the
Company, including disks and other storage media, filing cabinets or other work
areas, is subject to inspection by Company personnel at any time with or without
notice. Prior to leaving, I will cooperate with the Company in completing and
signing the Company's termination statement.

7.    LEGAL AND EQUITABLE REMEDIES. Because my services are personal and unique
and because I may have access to and become acquainted with the Proprietary
Information of the Company, the Company shall have the right to enforce this
Agreement and any of its provisions by, injunction specific performance or other
equitable relief, without bond and without prejudice to any other rights and
remedies that the Company may leave for a breach of this Agreement.

8.    NOTICES. Any notices required or permitted hereunder shall be given to the
appropriate party at the address specified below or at such other address as the
Party shall specify in writing. Such notice shall be deemed given upon personal
delivery to the appropriate address or if sent by certified or registered mail,
three (3) days after the date of mailing

9.    NOTIFICATION OF NEW EMPLOYER. In the event that I leave the employ of the
Company, I hereby consent to the notification of my new employer of my rights
and obligations under this Agreement.

10.   GENERAL PROVISIONS.

10.1  GOVERNING LAW; CONSENT TO PERSONAL JURISDICTION. This Agreement will be
governed by and construed according to the laws of the State of California, as
such laws are applied to agreements entered into and to be performed entirely
within California between California residents. I hereby expressly consent to
the personal jurisdiction of the state and federal courts located in San Diego
County, California for any lawsuit filed there against me by Company arising
from or related to this Agreement.

10.2  SEVERABILITY. In case any one or more of the provisions contained in this
Agreement shall, for any reason, be held to be invalid, illegal or unenforceable
in any respect, such invalidity, illegality or unenforceability shall not affect
the other provisions of this Agreement, and this Agreement shall be construed as
if such invalid, illegal or unenforceable provision had never been contained
herein. If moreover, any one or more of the provisions contained in this
Agreement shall for any reason be held to be excessively broad as to duration,
Geographical scope, activity or subject, it shall be construed by limiting and
reducing it, so as to be enforceable to the extent compatible with the
applicable taw as it shall then appear.

10.3  SUCCESSORS AND ASSIGNS. This Agreement will be binding upon my heirs,
executors, administrators and other legal representatives and will be for the
benefit of the Company, its successors, and its assigns.




                                       3.
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10.4  SURVIVAL. The provisions of this Agreement shall survive the termination
of my employment the assignment of this Agreement by the Company to any
successor in interest or other assignee.

10.5  EMPLOYMENT. I agree and understand that nothing in this Agreement shall
confer any right with respect to continuation of employment by the Company, nor
shall it interfere in any way with my right or the Company's right to terminate
my employment at any time, with or without Cause.

10.6  WAIVER. No waiver by the Company of any breach of this Agreement shall be
a waiver of any preceding or succeeding breach. No waiver by the Company of any
right under this Agreement shall be construed as a waiver of any other right.
The Company shall not be required to give notice to enforce strict adherence to
all terms of this Agreement.

10.7  ENTIRE AGREEMENT. The obligations pursuant to Sections 1 and 2 of this
Agreement shall apply to any time during which I was previously employed, or am
in the future employed, by the Company as a consultant if no other agreement
governs nondisclosure and assignment of inventions during such period. This
Agreement is the final, complete and exclusive agreement of the Parties with
respect to the subject matter hereof and supersedes and merges all prior
discussions between us. No modification of or amendment to this Agreement, nor
any waiver of any rights under this Agreement, will be effective unless in
writing and signed by the Party to be charged. Any subsequent change or changes
in my duties, salary or compensation will not affect the validity or scope of
this Agreement.

      This Agreement shall be effective as of the first day of any employment
with the Company, namely:
11/19, 1999
-------------


      I HAVE READ THIS AGREEMENT CAREFULLY AND UNDERSTAND ITS TERMS. I HAVE
COMPLETELY FILLED OUT EXHIBIT -1 TO THIS AGREEMENT.



Dated:    11/19/99
      ----------------------------


/s/ J. HENTRICH
----------------------------------
(Signature)

----------------------------------
JOHN HENTRICH


ACCEPTED AND AGREED TO:

WEBSIDESTORY

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

[ILLEGIBLE]
----------------------------------

By:    /s/ [ILLEGIBLE]
       ---------------------------

Title: CHIEF OPERATING OFFICER
       ---------------------------

Dated: NOV. 19, 1999
      ----------------------------

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                                    EXHIBIT 1

                         LIMITED EXCLUSION NOTIFICATION


THIS IS TO NOTIFY THE EMPLOYEE in accordance with Section 2872 of the California
Labor Code that the foregoing Agreement between the Employee and the Company
does not require the Employee to assign or offer to assign to the Company any
invention that the Employee developed entirely on your own time without using
the Company's equipment, supplies, facilities or trade secret information except
for those inventions that either:

1.    RELATE AT THE TIME OF CONCEPTION OR REDUCTION TO PRACTICE OF THE INVENTION
      TO THE COMPANY'S BUSINESS, OR ACTUAL OR DEMONSTRABLY ANTICIPATED RESEARCH
      OR DEVELOPMENT OF THE COMPANY;

2.    RESULT FROM ANY WORK PERFORMED BY THE EMPLOYEE FOR THE COMPANY.

      To the extent a provision in the foregoing Agreement purports to require
the Employee to assign an invention otherwise excluded from the preceding
paragraph, the provision is against the public policy of this state and is
unenforceable.

      This limited exclusion does not apply to any patent or invention covered
by a contract between the Company and the United States or any of its agencies
requiring full title to such patent or invention to be in the United States.


      I ACKNOWLEDGE RECEIPT of a copy of this notification.


                                      /s/ J. HENTRICH
                                      ---------------------------------------
                                       JOHN HENTRICH


                                      Date:    11/19/99
                                           -----------------------------------
WITNESSED BY:


-----------------------------------
(PRINTED NAME OF REPRESENTATIVE)






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                                   EXHIBIT - 2

TO:         WEBSIDESTORY

FROM:       JOHN HENTRICH
DATE:       11/19, 1999
SUBJECT:    PREVIOUS INVENTIONS

      1.    Except as listed in Section 2 below, the following is a complete
list of all inventions or improvements relevant to the subject matter of my
employment by BAKER & McKENZIE (the "Company") that have been made or conceived
or first reduced to practice by me alone or jointly with others prior to my
engagement by the Company :

     [X]    No inventions or improvements.

     [ ]    See below:



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

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

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


     [ ]   Additional sheets attached.

      2.    Due to a prior confidentiality agreement, I cannot complete the
disclosure under Section I above with respect to inventions or improvements
generally listed below, the proprietary rights and duty of confidentiality with
respect to which I owe to the following party(ies):

<TABLE>
<CAPTION>

        INVENTION OR IMPROVEMENT       PARTY(ies)      RELATIONSHIP

<S>                                    <C>             <C>
1.
  -----------------------------------  -----------     -------------------------


2.
  -----------------------------------  -----------     -------------------------

3.

  -----------------------------------  -----------     -------------------------
</TABLE>

     [ ]       Additional sheets attached.



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