DRAFT DRAFT DRAFT
If that sounds too esoteric, let me give you a couple of examples of how I use it routinely.
What didn’t load? With the Net button depressed and the Log option unchecked, I can see every file that didn’t load or otherwise caused an error all in a list.
Troubleshoot CSS. Even though I use CSSEdit as my primary tool for crafting the style sheets that shape a page’s layout and appearance, I also manipulate them by hand. The CSS button lets me spot errors according to Firefox’s parser, and click a link at the rigth to open the CSS sheet in Firefox scrolled to the line that has the alleged error.