Thanks for the help. Problem solved, I think...;-)
Giving the width to the #mainContent div was the answer. Removing the float for that div broke the site in Firefox. Maybe it was the way I did it. Never underestimate my clumsiness with code. Turns out, though, that it works with float left in.
Anyone tell me why this is an issue in IE7? Sometimes I think IE7 is the next IE6 but that's just my experience.
Hope you all have a great weekend. It's been amazingly cold here in Southern Vermont this weekend. Struggling to keep warm.
Thanks for your amazing help and your wonderful community.
All the best,
PS If it still looks bad in your browsers, let me know. BTW, what do you guys like for browser testing?