Try jumping on over to
http://www.w3schools.com/css/default.asp
All you ever wanted to know about css and you can use "try it yourself" to see how it works.
You can also take a book whose formatting you admire and take a look at it in code view and copy its stylesheet in place of the existing one and alter your text to use anything special.
As always, work on a duplicate copy in case something goes wrong.