Display CSS in its full style

I wanted to add a style to a div, but I was sure that our extensive CSS would have a class I could use, thus saving myself from increasing the size of the CSS file. However, how would I be able to view all the different styles and classes in the style they were assigned to? This would enable me to be able to quickly find the style I wanted and apply the class.

Couldn’t really find anything, so I quickly knocked one up.