The Web Application Stress Tool is a free utility from Microsoft designed for testing web sites. You can get it as part of the Windows 2000 Server Resource Kit. It is an excellent product and useful for both measuring the maximum load that your web site can handle and for stressing your web site to see if there are any errors in your code.

Essentially you turn on recording and then just navigate through your web site doing all the things that a visitor would normally do. After recording you can play the visit back again. You can adjust the number of simultaneous visitors, the speed of their connections and many other parameters. We have caught a number of bugs in our sites using this tool. You will too.