Good Toy
For any geek who’s interested in the structure of a web page they’re looking at, try Aardvark. (You are using Firefox, aren’t you?). It rocks. Once turned on, you can roll the pointer over an element to see the bounding box, the type and the CSS class and/or id, if any. Also you can see the source, muck about with widths, turn off elements and so on. Very nifty - well worth a look.