OK, I've had a look at your stylesheet. This is not the way I've normally seen it done but that's not to say your method is "wrong". Usually the font specs are done with @font-face statements at the top of the css file.
What does look wrong is that you have a missing semi-colon at the end of each line before:
Code:
src: url(res:///Data/fonts/somefontname.ttf);
Try correcting all those first.
If you still have no joy then I'll attach an edited stylesheet in the way I would have done it.