IE6 prior to Service Pack 2 fails to stop the popups when this page loads. This is because the page contains the body onload tag to execute the javascript popup function when the page loads.

In Firefox, the popup blocker stops this (the IE6 SP2 popup blocker also stops the popups but...) If you click the following hyperlink in IE, you will still get 30 bouncing pages pop up:

This makes a good screensaver (clicky-poo)

Also, if you have Firefox set to block annoying javascripts, the windows will not travel all over the screen (but they'll still pop up)