Does anyone know how to do it on a Mac? If there's actually a place where this is sated, can someone please link me to it?

There is a nifty extension for Firefox called Firebug. I have no idea whether it works on a Mac, though. Once you have it installed, you can right click the overlay and select "Inspect Element" from the context menu. Using Safari, you would probably have to open the source code (somwhere under View) and search for style tags.

Oh dammit, okay, thanks. I'll figure something out.