CSS gets pretty addicting once it begins to make sense. The very first thing, when contemplating a CSS layout is to ALWAYS remember CSS-P is a study in "relationships!"
You will be telling certain page elements to "go stand over there" and others to "move over here." And then, you will be telling them to keep their distance from each other. Others you will just let "go with the flow!" It can quickly become a jumbled mess unless each element is also given instruction on how it relates to the other page elements.
The best way to learn is start simple: learn to position two <divs> in various combinations. Keep them seperate at first, and then try nesting them.
Don't change more than a few values at a time. View the changes and then test some more. Once you begin to understand the "relationships" that encompass CSS-P (positioning) as well as the BOX MODEL properties, it will become much easier.
One almost universal truth with CSS is that there are often a number of ways to accomplish a task. The flexibility is tremendous!
Keep it simple at first, play around with the code and learn from experimenting. Try doing a search for CSS layouts and start "tweaking" one to fit your needs.
We'll talk... ;)