If you’re a web designer (at any level) or someone that maintains a blog or website, one of the essential skills to have is a basic understanding of HTML and CSS. HTMLDog.com is a site that I highly recommend bookmarking and referencing on a regular basis. Although I have my own web design training course, I often recommend my members learn the basics through HTMLDog.com (first). The structure and the easy text-base tutorial examples are perfect for learning and understanding the foundation of HTML and CSS. I HIGHLY RECOMMEND studying from this site.
Also, you might be interested in picking up the book from Amazon.com.