There’s couple of cool online tools to compress or beautify your CSS.
First one being www.codebeautifier.com, which handles both. You can select your compression level, from lowest (beautified CSS) to highest (smallest size, harder to read). You can also select different kinds of options with your compression / beautification.
Another really cool tool is www.csscompressor.com, where again you can select compression level and proper options.
Both tools shows you possible error messages and the compression ratio.
For my example compression, it removed 284 bytes, which doesn’t seem so much, but when looking at the total number, it’s 15,6% of the original size! That’s impressive.
Compression ratio: 1.538KB/1.822KB = 15.6% (-284 Bytes)
YSlow allows you to optimize CSS, JS (and also beautify) , smush images using Yahoo Smush.it and it also shows your sites grade with tips on how to improve speed.