Most companies require that you have at the very least a highschool diploma; however, they would prefer if you have a bachelors degree in computer graphics, code formatting, and of course editing. The first two are obvious components, but the third one might throw you for a loop. Editing and revising is a major part of making webpages, afterall you wouldn't want something incorrect to be seen by potential clients. And as in many other fields experience can sometimes outweigh sheer education.