Facebook fan box plugging not displaying in firefox

I installed a Facebook fan box plugging on my wordpress site but in firefox it doesn’t display properly. Instead I see this page in the iframed box http://www.facebook.com/connect/connect.php. With Internet Explorer 8 it is displaying correctly but in firefox it doesn’t work. Where should i look forward to fixing the problem? In plugging coding, in my hosting, in my wordpress or somewhere else?

Thanks!