Ultra-Foxiness

A very informative advanced tweaking guide for Firefox can be found here. In addition to a pretty comprehensive walk-through of the about:config settings page, it also contains interesting and useful tidbits of information, such as this one:

Select only a portion of a web page by holding down the left mouse button or the CTRL key over the start of your selection, then dragging the cursor to the end of your selection and releasing the left mouse button/CTRL key. Now right-click on this highlighted selection, and in the context menu select 'View Selection Source' - the source window will open and only show the coding related to the portion of the web page you've highlighted. This is very useful if you don't want to wade through large chunks of code just to see how a neat effect works on a page, or if you can't figure out which portion of code relates to which section.

I have linked directly to page 8 of the guide, where the Advanced Tweaking section starts, since the first seven pages are a bunch of simpleton explanations for basic features and procedurals. The advanced part, however, is well worth your time to read through and tweak your browser.