This is a strange one.
In my gallery, http://www.mypettalks.com/cpg1410/index.php, the theme is completely different when viewed in IE vs. Firefox. Completely different- layout, pictures etc. I've no idea why. Any ideas?
Can not replicate. They look the same to me in FF and IE. However, you should set "Max dimension of a thumbnail" in Coppermine's config to a value that makes sense, preferably "100", or you should run admin tools and re-create your thumbs. If you don't, your thumbs look silly and your content is too wide to fit on the screen.