Sure, Microsoft’s ineptness is legendary, but I dumped IE for one main reason: plug-ins (extensions, add-ons, name has changed a few times). The killer-app of plug-ins, the singulary sufficient reason to install Firefox would have to be WebDevleoper (about 280% better than the similarly named, but featurely-challenged IE Web Developer)

Below are my standard fresh-Firefox-install plugins. Note some overlap functionalities, for example WebDeveloper has equivalents for ViewSourceWith and MeasureIt — however, those include nifty buttons for your toolbar and that’s worth the intsall right there and WebDeveloper’s are somewhat buried. (yeah, that IS lazy of me)

• ColorzillaEyedropper for lifting colors from pages
• console2Basic JavaScript message console
• CSS ViewerHover over any page element to see basic CSS attributes
• downThemAllMuch improved download manager
• FirebugMUST HAVE! JavaScript, debugger, network traffic, and much more
• flashblockControl when Flash plays on pages
• measureItSimple ruler
• Pearl Crescent Page SaverSeveral options for screen snapshots to PNG
• ScreenGrab!Basic screen snapshots
• Tab EffectSpin-transition between web page tabs
• URL ParamsGreat debugging by editing get and post params
• viewSourceWithChoose how you View page source
• Web DeveloperMUST HAVE! For all web development. The King!
• ySlowShows page loading bottlenecks

Like I said, together this represents “can’t live without” them level of devotion.

Firebug is much like Fiddler but simplier