So one of the things I’m quickly learning at work is the implications of CSS coding strategies and how they relate to site performance. I’ve long been a fan of descendant selectors as they tend to allow leaner markup. However, there are serious speed ramifications when relying upon them in your CSS, notably rendering speed. Likely not an issue for smaller sites, but the speed implications become noticeable as your projects increase in scale. This is a great overview of how to write efficient CSS with rendering speed in mind.

Also, see this article on how Yahoo! and AOL use CSS sprites to speed things up, as well as this post written by Dave Hyatt regarding browser rendering, written while he was still at AOL.