Firebug is a great add-on to work with firefox.

Firebug a very very useful tool for web designers and developers to understand the coding behind the web page.

Basically by using this addon you can view the source code of a block, textbox or any element on a page.

And the BEST thing is that you can EDIT THE CODE directly there only.

You can download and install this add-on from the following url

https://addons.mozilla.org/en-US/firefox/collection/firebug_addons

After installing firebug, restart your browser.

Now right click on page, you will see a one more option “Inspect Element”

Firebug Firefox addon
Firebug Firefox addon

Now when you will click on Inspect Element then it will show you a screen, which will display the hierarchical structure of all the source code. You can see the code of any element.

Firebug Firefox Extension
Firebug Firefox Extension

Firebug Home page : https://addons.mozilla.org/en-US/firefox/collection/firebug_addons