<PAGE>
                                                                       EXHIBIT 1

                       SCHEDULE 13D JOINT FILING AGREEMENT

         The undersigned and each other person executing this joint filing
agreement (this "Agreement") agree as follows:

         The undersigned and each other person executing this Agreement are
responsible for the timely filing of such Schedule 13D and any amendments
thereto, and for the completeness and accuracy of the information concerning
such person contained therein; but none of the undersigned or any other person
executing this Agreement is responsible for the completeness or accuracy of the
information statement concerning any other persons making the filing, unless
such person knows or has reason to believe that such information is inaccurate.

         This Agreement may be executed in any number of counterparts, each of
which shall be deemed to be an original, but all of which, taken together, shall
constitute one and the same instrument.

                                   * * * * * *

                              Page 1 of 3 Pages
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         IN WITNESS WHEREOF, the undersigned have caused this Agreement to be
signed by their respective officers thereunto duly authorized as of the date set
forth opposite their name.

Date: December 23, 2003

                                  TH LEE PUTNAM VENTURES, L.P.

                                  By:      TH Lee Putnam Fund Advisors, L.P.,
                                           its general partner

                                  By:      TH Lee Putnam Fund Advisors, LLC,
                                           its general partner

                                  By:    /s/ James Brown
                                         -------------------------------------
                                         Name:  James Brown
                                         Title: Managing Director

                                  TH LEE PUTNAM PARALLEL VENTURES, L.P.

                                  By:      TH Lee Putnam Fund Advisors, L.P.,
                                           its general partner

                                  By:      TH Lee Putnam Fund Advisors, LLC,
                                           its general partner

                                  By:    /s/ James Brown
                                         -------------------------------------
                                         Name:  James Brown
                                         Title: Managing Director

                                  TH LEE PUTNAM FUND ADVISORS, L.P.

                                  By:      TH Lee Putnam Fund Advisors, LLC,
                                           its general partner

                                  By:    /s/ James Brown
                                         -------------------------------------
                                         Name:  James Brown
                                         Title: Managing Director

                                  TH LEE PUTNAM FUND ADVISORS, LLC

                                  By:    /s/ James Brown
                                         -------------------------------------
                                         Name:  James Brown
                                         Title: Managing Director



                              Page 2 of 3 Pages
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                                  TH LEE GLOBAL INTERNET MANAGERS, L.P.

                                  By:      TH Lee Global Internet Advisors, LLC

                                  By:    /s/ James Brown
                                         -------------------------------------
                                         Name:  James Brown
                                         Title: Managing Director

                                  TH LEE GLOBAL INTERNET ADVISORS, LLC

                                  By:    /s/ James Brown
                                         -------------------------------------
                                         Name:  James Brown
                                         Title: Managing Director

                                  THLI COINVESTMENT PARTNERS, LLC

                                  By:      TH Lee Putnam Fund Advisors, L.P.,
                                           its general partner

                                  By:      TH Lee Putnam Fund Advisors, LLC,
                                           its general partner

                                  By:    /s/ James Brown
                                         -------------------------------------
                                         Name:  James Brown
                                         Title: Managing Director

                                  BLUE STAR I, LLC

                                  By:    /s/ Thomas H. Lee
                                         -------------------------------------
                                         Name:  Thomas H. Lee
                                         Title: Managing Member

                               Page 3 of 3 Pages

