The thickbox didn't work the first time I tried it with Firefox - it brought me to a new page.
Whether it works as a way of displaying info depends on how used to seeing it your users are (for example, will they use the back button to get out of it?). Personally, I don't like them...but that's just my opinion
There are a few other things you probably need to take a look at with Firefox , such as links having the default blue underline on the Specials page.