If you have worked in web application development, even a little bit, you have had to deal with forms. I have had to learn quite a lot about this surprisingly complicated topic lately, for work on our Ladybug software. Sounds like a good candidate for a crib sheet like 10 Tips to a Better Form.
Incidentally, does anyone have a definition for crib sheet? I think I know what it means, but cannot find a definition anywhere. In fact, one of the first results Google gives me for crib sheet is another CSS Crib Sheet!