Tweak CSS to perfection
Firebug is a add-on for Mozilla Firefox that integrates with Firefox to put a wealth of development tools at your fingertips while you browse.
You can prank your friends by showing them an edited website.
Firebug is free and open source (BSD)
Monitor network activity
Quickly find errors
bookmarklet and whenever you will click it, Firebug will open in the webpage.
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