One of my recent projects has been geekwagon.net. It's a website that is pretty much useless, but gives me something to code by hand to figure things out. Today I came across this article about bad html and css.
Other than the bullet about flash dependency, I think I've broken every one of these dang rules. I found the part about "visual thinking" the most eye opening. That is pretty much how I've always done websites. First figure out how I want it to look, then make a structure that conforms to it. That paragraph changed the way I will make websites from now on. Worth a read.