About CSS

I just wanted to know is there any place where I can find all of the prefix in CSS about making new style like this:

.messageContentInner {background: url(../images/anotherwow/rightBottomCorner.png) no-repeat right bottom; }

I am talking about this .messageContentlnner for adding more images :? I need more places like this i want to cr8 a new great style... Please help me