A definitely must read tutorial on learning HTML and CSS is Sitepoint's "Learn HTML and CSS: An Absolutely Beginner's Guide. It covers the tools of what you need to get started and explains the anatomy of your first web page.
Here are some websites to get you started learning HTML.
We recommend that you start by going through both the HTML and the XHTML tutorials at w3schools.com.
XHTML is a newer version of HTML and is the version that you should strive to use when you code your web pages. Nevertheless, the HTML tutorials will provide a good foundation of knowledge that you will need.
To be more precise, HTML 4.0 is the last version of HTML. The version that came after HTML 4.0 is known as XHTML 1.0. As of this writting in 2008, XHTML 1.0 is the newest version currently out.
Another good place to begin is the HTML beginner guide at htmldog.com
As we have mentioned that you should learn CSS alongside with HTML, you should visit their CSS beginner guide next. There you will learn about CSS selectors and the box model.
After learning the basics, follow through with their CSS. And then the advanced HTML and CSS tutorials.
The HTML reference at sitepoint includes mentions of the difference between HTML and XHTML.
The Sitepoint CSS Reference start by explaining what is CSS and covers basic syntax, specificity rules, box properties, filters and hacks, and more.
It includes an alphabetical list of properties as well as a series of live demos where you can change and test out CSS rules.
W3Schools has a series of tutorials on CSS that you can go through.
This is a step-by-step tutorials for learning selectors.
