I don't think it can be done in CSS, since html doesn't parse within a textarea, so the usual css jump with ids doesn't work!
If I'm not mistaken there isn't a way to do this in javascript, but I actually can't say, since I never had to do this type of stuff, css jumps were the best solution.
Try posting this in the javascript forum, or maybe the admins/mods will move the thread!
EDIT: maybe if the textarea was initially in a div, then swapped into a textarea once the id was found?