Ok tool I guess but at least Firefox users already have enough. Firebug, Web Developer Toolbar can do this and more. The 2 browser interface, well also covered thrugh extensions like IETab or just a matter of changing windows. Does too little but perhaps useful for IE users who have no clue or desire for Firefox/Mozilla stuff - or Opera users... I belive it run Firefox as activeX embedded somehow - see folder of Site Inspector, only reason it ask for where your FF is installed is because of toolbar. What version of FF is used for rendering what you see? I think old one so may be not even useful, 1.0.x is not supported any more.