Now that is very interesting, I've just cleared my FF cache and I get the same thing.
The text is the alt tag from the images not yet loaded, so I wonder if I some kind of formatting error. Now the page is cached again I'm not seeing the problem when I go back.
I can't remember the site doing this before I made all the changes yesterday, so I can only assume I've broken something, or the server is being a bit slow in presenting the images and FF initially thinks they are missing.
Hmmmm, wonder what to do?
Cheers
Cris.