[jonathan lall]

Chances are that you made a really small syntax error in your HTML code's link, or possibly (but unlikely) in the CSS file itself. FrontPage (and IE) tends to be very forgiving of mistakes or bad code, which is why this is probably the case.

If you have this page uploaded on a web server, I'd be happy to take a look. It's likely that the problem lies in your <link> or <style> tags, or their attributes though, so double-check them first.