Sadly in Windows phone 7, although the font-face tag is supported it’s not possible to link to external fonts. This means that you can’t get WOFF fonts that are not on the phone by default working in IE9 for Windows Phone. There are 16 differences between IE9 and IE9 for WP7 this being one of them. If you want to check out the other differences I wrote this blog post for Ubelly a few weeks ago.