Firstly there's Creative Journal CSS, a mammoth tutorial that takes you from the very basics of HTML/CSS to coding your own snazzy looking journals over at deviantart.
It's incomplete, and what has been written needs editing, so take care in there ok?
Secondly there's User Stylesheet Tutorial, a tutorial I began some time after 'finishing' my black skin for deviantart. I stopped writing this to start work on Creative Journal CSS, so it's missing all the case studies of skinning deviantart - but the basics are there.