I was annoyed with Firefox 2 always stealing back the PCs focus after I clicked a link outside the browser, or tabbed to a new program.
A 5 second Google search later found this page with excellent advise on how to fix this problem. It also shows how you can alter almost any of the setting in Firefox!
(edit): And another here which speeds Firefox up.
http://public.ccsds.org/sites/cwe/help/ … aspx?ID=10