Good news.
Your issue, as I expected, has nothing to do with IFrame.
Your links' HREF attribute value is improperly formatted - instead of forward slashes, you've used back slashes - i.e. instead of http://www.abet-laminati.it you have http:\\www.abet-laminati.it
While IE tries to fix errors when it sees it, FF and the rest of browsers do not make such attempts. As a result, your links work in IE and don't work in FF
Fix it and you'll be all good!