What is Firebug?
Firebug is always just a keystroke away, but it never gets in your way. You can open Firebug in a separate window, or as a bar at the bottom of your browser. Firebug also gives you fine-grained control over which websites you want to enable it for.
Firebug makes it simple to find HTML elements buried deep in the page. Once you've found what you're looking for, Firebug gives you a wealth of information, and lets you edit the HTML live.
Firebug's CSS tabs tell you everything you need to know about the styles in your web pages, and if you don't like what it's telling you, you can make changes and see them take effect instantly.
When your CSS boxes aren't lining up correctly it can be difficult to understand why. Let Firebug be your eyes and it will measure and illustrate all the offsets, margins, borders, padding, and sizes for you.
Just the way you like it
Using Firebug gives a lot of possibilities for web development to your hands. Though you're feeling something is not working as you would like it to? No problem. Firebug offers a lot of options to adjust it to your needs.
Search and you shall find
Sometimes you know what you're looking for, but you can't see it in the panel. Using the quick search box in Firebug's toolbar you can search inside Firebug's panels and see the results highlighted as you type.
Firebug allows to view and manage cookies in your browser. You can deny cookies for specific sites, filter cookies, create new and delete existing cookies. You can also break into the debugger when specific cookie changes its value and see the line of script that caused the change.