Have you ever worked on a web application that just didn’t work in Firefox? Many companies still use IE exclusively internally and any web application they develop will never be tested on another browser. This makes debugging client side script very challenging (unless you enjoy the pain of dealing with the Microsoft Script Debugger). Personally, I don’t enjoy the dreaded “Object Error” that seems to be just about the only error IE is capable of displaying. Enter FireBug Lite: A FireBug version that works in IE. Sure, it is a bit more work (to use it you have to include a JavaScript file) but it is way better than anything Microsoft currently has. Check it out: http://www.getfirebug.com/lite.html.