If you've never toyed with Firefox, one of the major features you're missing -- especially if you're in IT -- is the add-ons. Add-ons don't merely let you tune Firefox to better fit your browsing style. In fact, some extensions are applications in their own right. A number of add-ons have become so critical to my daily work that they preclude the use of any other browser. Some are related to Web development, but others are more general-purpose. Here are my top ten (or so).