<PAGE>   1
                                                                   EXHIBIT 10.66

                                    AGREEMENT


         THIS AGREEMENT ("AGREEMENT") is made as of February 19, 1999, by and
among TCI.NET, Inc., a Delaware corporation ("TCI.NET"), TCI Internet Services,
Inc., a Delaware corporation ("Internet") and Tele-Communications, Inc., a
Delaware corporation ("TCI" and, collectively with TCI.NET and Internet, the
"TCI Parties") and Bruce W. Ravenel ("Employee Stockowner").

         WHEREAS, the Employee Stockowner is the grantee of an option (the
"Option") under an Option to Purchase Common Stock Agreement, dated as of
December 1, 1996 (the "Option Agreement"), among the Employee Stockowner,
TCI.NET and TCI, pursuant to which he acquired 4 shares of Common Stock, $1.00
par value per share, of TCI.NET (the "Shares");

         WHEREAS, the Employee Stockowner is also party to a Stock Appreciation
Rights Agreement, dated as of December 1, 1996 (the "SAR Agreement"), with
Internet and TCI;

         WHEREAS, TCI.NET and Internet are subsidiaries of TCI;

         WHEREAS, the parties hereto have reached an agreement regarding the
purchase and sale of the Shares, the cancellation of the Option and the
termination of the Option Agreement, and an amendment to the SAR Agreement;

         NOW, THEREFORE, in consideration of the premises and for other good and
valuable consideration as set forth herein, the receipt and sufficiency of which
is hereby acknowledged, the parties hereto agree as follows:

         1. Share Repurchase. The Employee Stockowner hereby sells, and TCI.NET
hereby purchases, all, and not less than all, of the Shares for an aggregate
purchase price of $95,720 (the "Purchase Price"). The Employee Stockowner hereby
acknowledges receipt of a check in the amount of the Purchase Price. TCI.NET
hereby acknowledges receipt of stock certificate number
____________________________________, representing the Shares, endorsed by the
Employee Stockowner in blank.

         2. Option Cancellation. The Option is hereby canceled and the Option
Agreement is hereby terminated. The Employee Stockowner hereby acknowledges that
he has no further rights, and TCI.NET has no further obligations, thereunder.

         3. SAR Amendment. The SAR Agreement is hereby amended to delete the
requirement outlined in paragraph 3 of the SAR Agreement that the Employee
Stockowner exercise his Option under the Option Agreement in order to exercise
his SARs (as defined in the SAR Agreement).


                                        1

<PAGE>   2



         4. Employee Stockowner Representations. The Employee Stockowner hereby
represents and warrants that:

            (i) he has the legal capacity to enter into this Agreement and
            perform his obligations hereunder;

            (ii) this Agreement constitutes his legal, valid and binding
            obligation; and

            (iii) the Shares represent all shares of common stock that he
            currently owns in any TCI Party other than TCI.

         5. TCI Party Representations. Each of the TCI Parties hereby represents
and warrants that: 

            (i) such party has all the requisite corporate power, authority and
            legal capacity to enter into this Agreement and perform its
            obligations hereunder;

            (ii) this Agreement has been duly and validly executed and delivered
            by such party; and

            (iii) this Agreement constitutes the legal, valid and binding
            obligation of such party.

         6. Binding Effect. This Agreement shall inure to the benefit of and be
binding upon the parties hereto and their respective successors and assigns.

         7. Construction. The section headings contained in this Agreement are
inserted for reference purposes only and shall not affect the meaning or
interpretation of this Agreement.

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

         9. Applicable Law. This Agreement and the legal relations between the
parties hereto shall be governed by and construed in accordance with the laws of
the State of Delaware without regard to the conflict of laws rules thereof.

                                       2
<PAGE>   3



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


TCI.NET, INC.

By:
   ---------------------------------
Name:
Title:

TCI INTERNET SERVICES, INC.

By:
   ---------------------------------
Name:
Title:

TELE-COMMUNICATIONS, INC.

By:
   ---------------------------------
Name:
Title:




EMPLOYEE STOCKOWNER

By:
   ---------------------------------
Name:


                                       3