Nice, I just spotted 2 firefox tips. One: http://www.mozilla.com/en-US/plugincheck/ — check if your plugins are up to date. Nice!
Two: you can disallow JavaScript to move / resize your windows. I knew there was a option (Edit > Preferences > Content) to enable/disable JavaScript, but if you click the “advanced” button there, you can have JS while disallowing all sorts of nasty behaviour. Makes for a more happy me :)
(Forgot where I got this from btw, let me check… here)