They must have coded their site to look/call for something that only IE has that exists outside of the IE engine. Which btw is how IE tab works, using the IE engine and wrapping it in a FF window.
They MUST be getting paid by M$ to do that since only a moron or greedy idiot would code a website only for IE, The buggiest, least secure browser on the planet. Unless of course someone higher up is getting the kickback and just mandating the use of IE only........