Strange things can often happen to web applications when they are under heavy loads.  It is, however, worthwhile taking the time to test your web application using an application such as OpenSTA (http://www.opensta.org/) or one of the commercial web testing offerings.

Recently I subjected one of my own websites to performance testing, and while the application performed well, I discovered that the default setting for the ADODB.Connection's timeout was quite low.  Increasing the timeout time ensured fewer users would ever see the timeout message. Whether they would stay around to wait for the page to load is another matter entirely!

While it is possible to write a quick Visual Basic application or script to repeatedly request the same URL via HTTP, it is advisable to test using an application that can perform real-world testing of your web application, such as performing searches on search facilities, logging in, submitting forms and other functionality.

Do not forget that it is very inadvisable to subject your live system to performance testing!