You use classes to identify parts of your HTML to which attributes need to be applied. Then in your stylesheet you define the classes. There is where you determine which attributes will be applied. There are a lot of different attributes. Be aware that ePUB2 uses CSS 2.0.1, so that determined which attributes could be used. Even then not all attributes will work though, some of them make no sense in eBooks and some of them will be ignored by readers. It is a fixed list though. For the complete specs, see:
http://www.w3.org/TR/CSS21/