To CSS or Not to CSS?

I am developing websites for a long time but I never really knew CSS that much. I know CSS and how I can do it, I've actually made some but my knowledge is only up to it's crust, but going deeper is a different thing so I've tried looking for an example. I was staring at the codes when I finally realized that I don't understand some of it and how and what it does.

I saw some great samples like the one making sub-menus and horizontal menu, vertical menu, etc.. and I was mesmerized to its capability. So now, I am compelled to study CSS - I hope I can comprehend. Wish me luck guys. By the way, I found some interesting sites that has truly great samples.

Dynamic Drive - feast your eyes upon CSS heaven.

I'll share more once I stumble into something great.