Your learn something new everyday. Today I learnt that CSS is case sensitive. No big deal. What I do find perplexing though is the fact that a) html attribute selection is case insensitive and b) alot of older browsers (or those running in quirks mode) implement CSS class selection as case insensitive. It is probably easiest to just use lowercase to avoid any potential issues with your stylesheets!

This article demonstrates 21 techniques you can employ to write usable CSS.