Firebug is one of those firefox extension which is pretty much unreplaceable and a tool that you simply can’t find a good substitute for in Internet Explorer, Safari or Opera. Developer tools do exist for these browsers, but firebug simply stand out in the pack.
Well, the meat of this post is about Internet Explorer and here’s the debugger tool named debugbar that is built with the attention to mimic what firebug is able to do in Firefox.
DOM Inspector: View DOM Tree and modify tags attributes and css attributes on the fly to test your page
HTTP Inspector: View HTTP/S request to check cookies, GET and POST parameters, view server info
HTML Validator: Validate HTML code to correct and optimize your code and html size of your page
And many more features: See page cookies, get pixel color on a page, make a page screenshot…