You may want to also look at
http://www.htmlhelp.com. I use it today mostly for a reference.
I have been programming HTML since the early days. You need to find a small project you want to work on and work on it till your happy with the results. Along with (X)HTML, learn CSS as well.
http://www.htmlhelp.com and
http://www.w3schools.com both have good guides/references.
Standards. Standards. Standards. One of the biggest things you need to learn right off the bat is to pay attention and adhere to the standards that are in place. Once your finished with your first project, make sure it validates.
The World Wide Web Consortium (w3c) provides a great validator for both HTML and CSS:
HTML:
http://validator.w3.org/
CSS:
http://jigsaw.w3.org/css-validator/