Cross Browser Issues?

[creativemuse]

I recently installed the "mt-plainjane" theme on my client's web site
(www.loosenupbodywork.com). It was working for a few days and all of a sudden the theme broke.

The "mainpane" has collapsed to the left side, showing 2 skinny columns. The strange thing is the page looks ok on Firefox 3, although looks broken on earlier versions of Firebox and IE.

My question(s):
(1) Are there any cross browser issues?
(2) Why would it all of a sudden change when there were no other changes to the theme?

Please help!

[kleinerChemiker]

maybe there is a broken entry that opens a tag and doesnt close it or close at tag, taht it doesnt open.

[yellowled]

I think there's one or more <img> tag(s) somewhere which isn't closed (<img ... />). At least that's what the W3C validator tells me. The images in questons all start with dmb_

YL