Disclosed is a method, system, and program for diagnosing a computer over a network, such as the Internet. A program, such as an applet, is provided that executes on the computer. The program causes the computer to download at least one object from a server over the network. Performance data is determined with respect to downloading the object from the server to the computer over the network in order to diagnose performance problems with the computer. The determined performance data is then transmitted to a diagnostic system over the network.