Probably best to start with XHTML so you can get the idea of what the different tags and do and the basic document structure. Then try adding some basic CSS and learn about selectors and the different CSS rules. I wouldn't jump straight into HTML5 and CSS3 because its more likely to be confusing since there are tons of new things. Best to just get you basic XHTML and CSS and get your head around how they both work together to create a web page. No point learning the new things before you get the foundations right. Once you learn these initial concepts everything (including HTML5 and CSS3) should flow together nicely.

CMS systems such as Joomla and Wordpress can be easy to use but difficult to set up. To really understand how they work requires a lot of development knowledge including the above and the addition of other concepts such as databases and server programming such as PHP - so definitely not for the faint hearted.