eZ publish layout is div based, this means that you can easily change layout using CSS techniques only. Good examples are in contribs section in Site Styles category so you can see what can be done without changing templates.
when skinning eZ you don't need to be an html expert, but you should have a good understanding of css. If you want to use your own html, you'll have to make your own complete pagetemplate / design. Not recomended unless you have some special demands.