I ran across these bad boys today. I’ve had similar types of documents in the past to use for reference while developing websites, but these look much more concise and easy to reference. These are cheat sheets for HTML and CSS. One page a piece. Definitely worth a look if you use HTML / CSS a lot.

http://www.ilovejackdaniels.com/cheat-sheets/html-cheat-sheet/

I would also suggest browsing around a bit more in that website, there are some other neato cheat sheets available and it’s a fun site in general.