Geographically distributed data-gathering client computers are connected to the Internet in the same manner as typical users (for example, via local dial-up connections). The data-gathering client computers poll a central server (the "UserMon" server) for a target site to access. After receiving the address of a target site from the UserMon server, the data-gathering client computers access the target site and obtain performance-parameter values indicative of the quality of their respective Internet connections to the target site and/or the performance of the target site itself. Each data-gathering client computer then pushes the performance-parameter values back to the "UserMon" server for analysis.