zulu_dude - 12:23 pm on Sep 14, 2011 (gmt 0)
I'd suggest getting a handle on at least one server side language, such as PHP. That goes very well with learning a bit of MySQL and once you've got the two skills combined you're straight away employable (to a certain degree!).
Granted, you're probably not thinking about employment at 13, but it's good to have a long term view!
As lucy24 has said, this assumes you've already got a handle on HTML/CSS.