Firefox/IE for Mac see something different.

I have been working on this site for about a month now and everything has been fine. But suddenly yesterday, a mysterious bar showed up between my main homepage graphic and the color box underneath it. But what's even weirder is that it only seems to appear in Firefox (or any of the Mozilla/Netscape browsers) and IE for Mac. Only for the Mac. IE and Firefox display it correctly on the PC. But Mac Firefox and IE displayed it correctly up until yesterday. I have scanned the code and can't find the source of it. Does anyone have any ideas? I can't seem to see anything that would cause this and it is driving me crazy!
The web address is:
http://www.adventurecycling.org

If you view it on a Mac with Firefox, Mozilla, Netscape, or IE you'll see what I'm talking about. (however Safari, Omniweb, and Opera work fine)

I'm guessing you recently added something to your right-hand column? Your table cells will make a grid that will stretch as high as the tallest element, so when you add something to one column, the others will grow to match. Your 'who we are -- what we do' table cell has a valign=bottom, so any extra space created will be above it. I think you'll be ok if you change that to a valign="top".

You were exactly right. I added that 'Bike Giveaway' image and it goofed it all up. I just added about 8 <br> and that seems to push it up to where it needed to be. Thanks for the help.

Lazerbrains