I find myself looking up CSS and PHP questions all the time and Google is usually my best friend. I happened to search around a little in app world for a mobile resource and came across Concentric Sky and their 3 cheat sheet apps.
They have cheat sheets for CSS, PHP, & Python available and they all store their info on the device so you are not reaching out to external resources. The information is searchable and it includes the descriptions and examples which is nice.
If you are a web developer and find yourself in need of a cheat sheet every once in awhile all of the guides are available for $2.99 each. Some of the information is a tad dated but these are open standards and change all the time.
