How do You make layotus and banners?

How do you make layouts and banners? I don't want any sites that make them I want sites that tell you how to make them. For the banners I know of alot of sights where u can make them but, they aren't that good and I want to make the really good ones. Please help me I want to know how? Go to my howrse profile page and check it out. Plz