Sheri German has created an excellent course for CSS and (X)HTML by collecting links to various CSS/HTML articles at Community MX and grouping them into a logical sequence. There is also a thorough description of the content and how it relates, making it extremely valuable. There are almost 2000 articles over at CMX now, and finding just the right article for what you need is getting harder, but if you are looking to generally improve your HTML and CSS skills, or learn from scratch, this is a perfect starting point. The article is free, and it lists both free and commercial articles: http://communitymx.com/content/article.cfm?cid=C71D9. Of course, if you subscribe to Community MX, they are all free.