Ouch! I'm guilty of as many as nine or ten of these, in various ways. Usability guru Jakob Neilsen writes about the top ten mistakes made by weblog authors, from a usability perspective.
I'd gone off Neilsen a bit. I learnt a lot from his work a few years ago, but I don't feel like he's added much to it recently. This, though, was very helpful to me. If you blog, go read.