I know the site works on my phones as they use Opera (Nokia 9500 and P900)/ IE Mobile (XDAii) so I tried a few online WAP emulators. Two of them came back with variants of wrong MIME type messages, e.g.
http://www.wapsilon.com/ says:
Wrong mime-type, I got text/html; charset=ISO-8859-1, but I want text/vnd.wap.wml.
This error occurs when you request a page that is not a WAP page, or when the webserver isn't set up correctly for hosting WAP sites"