I personally believe starting with PHP & MySQL may benefit you the most. I actually learned the basics of PHP & MySQL well before I even learned HTML/CSS. A bit backwards, and caused some bumps along the road. But I felt learning PHP & MySQL help me tremendously down the road. Picking up on other languages seems to be a bit easier with a small background in PHP & MySQL rather than strictly HTML/CSS.

Pick up some books from Sitepoint. Or grab a few ebooks. Start small, build your way up. It's more of an understanding rather than learning at first in my opinion. I tend to grab open source applications built with php, mysql and study them. Helps me out a ton!

Feel free to add me to MSN if you ever want to have a discussion, or need some help! I'm not a pro, but I do have an understanding.