Thanks for the tip on the tip on class identifiers, Friday. I did go through and change things sitewide, and it looks like they're all working again.
Thanks also to Tunnel7 and Paul for the advice. Going through some of the suggestions, I picked up on a LOT of important information regarding CSS. What I'm using it for barely scratches the surface, and I'm looking forward to learning more and REALLY putting CSS to use on our site
I'll be back!