Fantastic CSS Debugging Firefox Extension
I am known to say “WOW” quite often, but when I saw the Aardvark Firefox Extension, I said “FREAKING WOW!”. This is an absolutely fantastic extension that is sure to help you in debugging your CSS.
Simply go to the page you want to debug, and enable the extension by choosing Start Aardvark from the context menu. Now pass you mouse over the element you are trying to debug. The element will be outlined with a red border and you will see the element name, id and class name of the selected element. What is even better, there are a whole slew of keybord modifiers. For example press the *W* key and your selection will be made wider by showing you the containing element of the element you moused-over.
[link via mezzoblue]



I think using a bookmarklet is a more elegant solution. Check this one:
Mouseover DOM Inspector
http://slayeroffice.com/?c=/content/tools/modi.html
Works great with Firefox.
While I dont know if the bookmarklet is more elegant, it definitely gives you more information.
The two in conjunction are pretty nice. Thanks for the link Sérgio