Firebug is an extension for Firefox, but what happens when you need to test your pages in Internet Explorer, Opera, and Safari?
The solution is Firebug Lite to simulate some Firebug features in browsers that are not named "Firefox".
Firebug Lite creates the variable "firebug" and doesn't affect or interfere with HTML elements that aren't created by itself.
Find more info: http://getfirebug.com/lite.html
If you find issues, please report them: http://code.google.com/p/joomla-firebug/issues/list