WOW – I was looking around over the weekend and I found this STUNNING plugin – Tilt
It allows you to visualize the DOM in a 3D way so you can see the node containers from top to bottom. The possibilities are endless. it also allows you to visualize the STYLE sheets and DOM in a way firebug can only dream of….
WOW
Which comes from this
Tilting - OpenNTF
Here’s a video from the blog – still – WOW
Xomino 
This would be great if it worked on my company laptop but the video drivers are not capable of it. It works great on my desktop however.
You don’t need a plugin for that. 3D view should come with the latest version of Firefox (11).