So this isn't a new trick by any means, but it sure is handy (Think outlines, book chapters, line numbering...) The more markup you can minimize via CSS the better, in my book.

Until recently Firefox has always felt like a double-edged sword to me. The developer's add-ons have always been a pleasure to use. Firebug, ySlow, PageSpeed, Web Developer are all essential for web design. Unfortunately, my favorite, firebug, has been notorious for turning into a zombie and snacking on my computer's memory (that no amount of Left 4 Dead can solve!). Leave the browser open a couple hours and viola you have a standards compliant browser that runs slower than IE6.