It's a very useful web development tool that can help us to learn the HTML, CSS, or even javascript when we browse the net. Not only that we can read the codes, but also edit, debug and monitor them live. Just click on the item on the webpage, then the codes will be revealed. There, you can also edit the codes and see the changes.
The tool also provides network monitoring feature. It helps us to break down the files, so that we can speed up the web page loading.
By the way, it's an add-on to Firefox. You can just install it, and you can open the Firebug as a bar at the bottom of your browser, or even in a separate window.
Click here to download the free firebug.
