It's great that you now know at least some HTML, xHTML and CSS. I think that the next thing to learn could be HTML5.
Hopefully you also get some exposure to the Bootstrap framework, or something comparable, along the way as many sites use it.
If you are going for web design you should also become familiar with image editing software such as GIMP and/or PhotoShop or something similar.
It's been my experience that first a mockup of the site is created using GIMP (or whatever) which is then broken down into a template with HTML and CSS.
Once you have the HTML and CSS from the template you can start putting in server side technologies/languages which makes the site more power/intelligence.
“The strongest of all warriors are these two — Time and Patience.” ― Leo Tolstoy, War and Peace
I created my own website back around 2012; it was just a developer having fun. But, I had basic questions like what colors, fonts, how to place things where in a web page, etc. I had found some useful information at that time, and presently the current web design and development trends, articles and books etc., at this website: https://www.smashingmagazine.com/
I'm a beginner too, so take my advice for what you will. But, I started getting into web development last year and found some great online (free) modules to work through. You might check out Codecademy and FreeCodeCamp, if you haven't already.
As someone else mentioned, starting to get familiar with Bootstrap along the way seems like a great idea. That's one of the things I'm doing right now also. That FreeCodeCamp site covers the basics of it.