CSS is great, but can be a huge pain in the rear. Things that seem so simple in HTML, and things that work across the board with HTML, you'll find is no the case when it comes to CSS.
CSS allows some flexibility, but you'll find that aligning things for example in HTML, are aligned the way you want them to be (if you've used validated standard html)....while aligning something in CSS, will align it properly in IE, and break in FF, or vice versa, which you then have to find CSS hacks for, etc.
For now, stick with HTML and learn it well. Then when you're ready to advance into the frustration of CSS....go for it.