Yes, Javascript should be the thing you learn after HTML and CSS. Byrne's link is the one I would have suggested, too.
EDIT: Oh, and just FYI, HTML and CSS aren't programming languages. Those are things like Javascript and PHP. I learned C++ after HTML and CSS, then got into PHP. Once you learn one programming language, you can pretty easily jump to another. The syntax may be different, but most everything else tends to work in a similar way.