Firebug is a surprisingly powerful add-on for the Firefox web browser. Aimed at web developers, Firebug lets you examine and edit the code of your web pages in your browser window. It also allows you to examine
The add-on comes into its own with CSS in particular. Firebug lets you see at a glance which rules of CSS apply to a particular element. Testing different rules no longer involves laboriously changing code in an editor, uploading it to your web space and refreshing the page every time you want to try something out. You can input the new code in Firebug and immediately see how it will affect the page you’re working on.
Despite being an add-on itself, Firebug is meaty enough to support its own add-ons, expanding its functionality — providing information specific to a package such as Drupal, for example, or adding reference materials.
As well as being a development tool, Firebug can also enhance your understanding of web programming by allowing you to view the code of any exiting website in detail. Unlike the “View Source” command, which only gives you a limited glimpse into the underlying workings of a web page, Firebug supplies considerable detail about each element so you can quickly gain an understanding of how a particular look or function was achieved.