Regarding the subSilver theme

It's been nearly a year since I made a new phpBB skin, I've forgotten quite a bit. One such thing I've forgotten is how to get rid of the borders around the category headings.

http://www.latourblanche.ca/kahve/phpBB2/index.php here's what I've done with the skin so far. (not really all that much) - as is now, the said border is something white...
http://www.latourblanche.ca/kahve/phpBB2/templates/subSilver/subSilver.css style sheet

I know the solution is blatantly obvious, but alas, my memory sucks.

Thanks. :)