Apply CSS coding conventions

I went through the CSS to apply CSS coding conventions: 4 spaces indentation, space after colons, and did a little bit of nesting when it made sense.

PS: This is my first pull request, yey!

![Awesome cat](https://f.cloud.github.com/assets/85783/572934/50fead24-c7a6-11e2-9e7a-e1ff4832ae52.gif)