This is a really simple tip, but also very helpful. If you don't like unwanted popups (and if they're "unwanted," I'm betting you don't), check out this very simple tip to stop them. Basically, Firefox has pretty good built-in popup blocking, but some people found that they could use Flash to initiate a popup window, circumventing Firefox's protection. This is the reason you may be experiencing those unwanted popups. But Firefox has a built-in ability to prevent plugins like Flash from creating popup windows - you simply have to turn it on. Pete Bevin has the details.