I have been going through this same process for a while and can give a couple pointers. First Like fuzzybunny said, you have to learn CSS and XHTML at the same time, since either one is pretty much useless, today, without the other, for any practical purposes.
Now let me save you some time. First, before CSS, you need to learn XHTML because the very purpose of CSS is to style the content you create in HTML. XHTML is the more recent version of HTML. Because the transition from HTML to XHTML is recent, every book and video on the topic feels they need to inform you of the difference, so they tell you the current way to do it (XHTML), then the old way to do it (HTML). knowing how sites used to be coded is useful, but there is no reason to spend as much time learning the wrong way to do it as the right way, plus, it is confusing when you are a newb. So the point of the meandering paragraph is to make certain you get a recent book on XHTML, and don't get confused trying to learn both XHTML and HTML, just focus on the XHTML and the CSS, and skim all the parts about the old way to do it so that you can recognize why you get validation errors when you apply certain tags in the body of the document.
So learn XHTML, and learn CSS together until you are good with those. I kept going back and forth between the two for a while. First I read XHTML, then CSS, then wen back and read more about XHTML to sort out the confusion between it and HTML, then back to CSS and spent quite a bit of time on CSS.
Next, learn how to incorporate Java Scripts into your site. Honestly, there is a ton of stuff you can add to your site without knowing how to write Java Script simply by cutting and pasting routines that are available on the internet. It is pretty simple to use, and a lot of routines just have you cut an paste some code into a couple spots in your web page. You are almost certain to run into opportunities to implement some copy pasta javascript into your sites while you are practicing your XHTML/CSS.
Now you can build a nice website, and this is pretty much where I am at. Next I plan to learn more about implementing Flash into a site and also more in depth knowledge about javascript. After that I will learn PHP or ASP and how to use them with MySQL databases.
At that point I think you should be able to do pretty much anything you want allowing you to make very nice websites.