I don't see the problem on my pc using firefox v3.6.13
I also checked in every other browser I have installed and didn't experience the problem (opera, safari, IE, chrome)
I can see the problem in FF on MAC though, but not on any other browser... I'm not sure what to do. It appears to be a bug in FF on mac and I don't know a work-around. I played around with the css for a half an hour or so and I couldn'd find a fix.