<PAGE>
                                                                   EXHIBIT 10.26

                             [VERTICALNET LOGO](SM)
                                 VerticalNet(R)

MICHAEL J. HAGAN
700 Dresher Rd., Ste. 100
Horsham, PA 19044
215-315-3115

April 23, 2001

Mr. Christopher Larsen
192 Dam View Drive
Media, PA 19063

Dear Chris:

I am pleased to confirm VerticalNet's employment offer to you. Details are as
follows:

JOB TITLE:                 Executive Vice President
REPORTING TO:              Michael Hagan, President and CEO
START DATE:                April 25, 2001

COMPENSATION

| |   Monthly base salary of $25,000 to be paid in equal installments on the
      15th and last day of each month. (Annualized $300,000). (For payroll
      purposes, you must start work prior to the 8th of the month to be paid on
      the 15th or the 22nd of the month to be paid on the last day of the
      month).

| |   You will be eligible to participate in the VerticalNet Executive Bonus
      Plan. Your annual bonus target will be 50% of base pay, payable at the
      discretion of the Board of Directors. For 2001, your bonus award will be
      guaranteed in the amount of $200,000, provided that you are still employed
      on the date that bonus awards are paid to other senior executives and
      remain employed by VerticalNet for at least 90 days following that date.

| |   You will be paid a starting bonus of $25,000, which you will receive in
      your second paycheck.

| |   Within 60 days of your Start Date, you and the CEO will mutually determine
      an annual bonus for you based upon performance metrics for VerticalNet,
      taking into account the overall compensation structure that you will
      establish for the overall VerticalNet sales organization.

| |   On April 27, 2001, you will be granted the option to purchase 400,000
      VerticalNet, Inc. shares of common stock, subject to vesting, at a price
      per share equal to the last trade on NASDAQ on the date of grant. They
      will vest 25% each six-month period, with full vesting on your two-year
      employment anniversary. These shares are granted to you pursuant to the
      terms of the company's Stock Option Plan.

EMPLOYEE BENEFITS

| |   You will be eligible to participate in the VerticalNet LLC 401(k) Plan on
      the first day of the calendar quarter (July 1) following your date of
      hire.

| |   You will be eligible to participate in the Employee Stock Purchase Plan
      effective October 1, 2001.


                                       1
<PAGE>

| |   You will become eligible to participate in VerticalNet's flexible benefits
      plan on the first day of the month following your date of hire, subject to
      the terms and conditions as stated in the Company's benefit plan
      documents. A Summary of Benefits is included in your new hire packet, with
      the exception that you will receive 4 weeks vacation. Questions regarding
      benefits should be addressed to Paige Tilley, our Benefits Administrator
      at 215-315-4313.

TERMINATION OF EMPLOYMENT

| |   If, during the 12 month period beginning on your Start Date, your
      employment is terminated by VerticalNet without Cause or by you for Good
      Reason, then in exchange for a general release, and in exchange for you
      being subject to the VerticalNet, "Employment, Confidential Information,
      Invention and Non-Competition Agreement" for a period of 6 months
      following your termination (which supercedes the time periods set forth in
      such agreement), (1) we will continue to pay to you your base salary for a
      period of 6 months following your termination, (2) we will pay to you for
      2001 your 2001 guaranteed bonus, and thereafter, your annual target bonus
      for the year in which your termination occurs, within thirty (30) days
      following your termination date, and (3) an additional 6 months of the
      vesting of your VerticalNet stock options will become immediately vested
      and all your vested options will remain exercisable for a period of at
      least 180 days following your termination. VerticalNet intends to enter
      into employment agreements with its senior executive officers within 90
      days, including you the COO and the other EVPs, and the agreement that you
      enter into may contain different (with greater or less of a benefit to
      you) terms than set forth herein, in which case you will receive an
      agreement with terms with that replace the foregoing matters that are no
      less favorable than the most favorable terms made to any officer of
      VerticalNet.

      For purposes of this letter agreement, "Cause" means (i) you are convicted
      of a felony, or (ii) in the reasonable determination of the Board, you
      have (w) committed an act of fraud, embezzlement, or theft in connection
      with your duties in the course of your employment with VerticalNet, (x)
      caused intentional, wrongful damage to the property of VerticalNet, (y)
      engaged in gross misconduct or gross negligence in the course of your
      employment with VerticalNet, or (z) you materially breached your
      obligations under this agreement or under any written confidentiality,
      non-competition, or non-solicitation agreement between you and
      VerticalNet, and shall not have remedied such breach within 30 days after
      receiving written notice from the Board specifying the details thereof.

      For purposes of this letter agreement, "Good Reason" means (1) if you are
      transferred, without your written consent, to a location that is more than
      50 miles from your principal place of business immediately preceding the
      transfer, (2) a material reduction of your authority, duties or
      responsibilities after you have provided us with reasonable notice and an
      opportunity to cure, or (3) any failure of VerticalNet materially to
      comply with and satisfy any of the terms of this letter agreement.

CHANGE OF CONTROL

| |   In the event of a Change of Control of VerticalNet, your vesting in any
      unvested options will be accelerated on terms that are no less favorable
      than the most favorable terms made available to any senior officer of
      VerticalNet other than the CEO. For example, if all unvested options of
      the COO of VerticalNet become fully vested upon a Change of Control, all
      of your options will become fully vested upon a Change of Control. For
      purposes of this letter agreement, "Change of Control" shall mean:

            (i) Any "person" (as such term is used in Sections 13(d) and 14(d)
      of the Exchange Act) becomes a "beneficial owner" (as defined in Rule
      13d-3 under the Exchange Act), directly or indirectly, of securities of
      VerticalNet representing more than 50% of the voting power of the then
      outstanding securities of VerticalNet; or


                                       2
<PAGE>

            (ii) The shareholders of VerticalNet approve (or, if shareholder is
      not required, the Board approves) an agreement providing for (x) the
      merger or consolidation of VerticalNet with another corporation where the
      shareholders of VerticalNet, immediately prior to the merger or
      consolidation, will not beneficially own, immediately after the merger or
      consolidation, shares entitling such shareholders to more than 50% of all
      votes to which all shareholders of the surviving corporation would be
      entitled in the election of directors (without consideration of the rights
      of any class of stock to elect directors by a separate class vote), (y)
      the sale or other disposition of all or substantially all of the assets of
      VerticalNet, or (z) a liquidation or dissolution of VerticalNet.

NEXT STEPS

This offer is contingent upon:

| |   Completion of a VerticalNet Employment Application (enclosed).

| |   Satisfactory evidence of your legal eligibility to work in the U.S. in
      accordance with the Immigration Reform and Control Act and completion of
      the "I-9" form which is included in this package.

| |   Your agreement that at no time following your Start Date will you use or
      disclose to any other person or entity any proprietary or confidential
      information about VerticalNet, or its parent, subsidiaries or affiliates,
      including without limitation, technical data, research, product, or
      business plans, products, services, projects, proposals, customer lists,
      software developments, marketing and financial plans, sales methods and
      systems, and financial information.

Please be aware that VerticalNet is an employer at-will. As a result, both you
and VerticalNet may terminate the employment relationship at any time, for any
lawful reason or no reason at all, with or without notice; provided, however,
that you will be entitled to receive the payments and rights set forth under the
"Termination of Employment" section upon the occurrence of the events set forth
under that section. Nothing in this offer letter or in any oral or written
statement creates a contract of employment or limits the right to terminate
employment at will.

If you have any questions concerning this or any other information, please feel
free to contact Monica Haley, Vice President of Human Resources, at
215-315-3297. We look forward to having you join the VerticalNet team!

Sincerely,


Michael J. Hagan
President and CEO

cc: Monica Haley
    Jim McKenzie

_____________________________________                ___________________________
Signature                                                      Date

_____________________________________
Social Security Number (required for Stock Option grant)


                                       3