It’s exceedingly rare that I read an article on code techniques and agree with absolutely everything that’s being espoused, but this article by Chris Coyier for Smashing Magazine is just that. In my opinion, this is a must read for all web developers that have to work in and around X/HTML code. My personal favorite: Eliminate unnecessary divs.
Sometime during the learning stages of Web design, people learn how to wrap elements in a div so that they can target them with CSS and apply styling. This leads to a proliferation of the div element and to their being used far too liberally in unnecessary places.
Oh yeah. And the example provided could not be more illustrative.
The others are spot on, as well, but this is my favorite because it’s less obvious and the single biggest source of code bloat, in my experience.