I often use Firefox beside my IE (currently version 6 and 7) during my development. Very often I need to test some page in both IE and Firefox. So I need to keep both browsers open together. But after I found very nice add-on for Firefox this is not the case anymore. Here it is. This allows to switch browser at runtime when Firefox is open. Woulld be good to have something like for IE too. Or maybe it already exists?