Do you have access to the CSS on the original site? If so, as Stevie says, add fallback fonts in you style sheet. E.g.
font-family:'BrownBold'<font color='"#FF0000"'>, 'century gothic', callibri, arial, helvetica, sans-serif</font>;
Those are just random fonts I typed, and it would be better to identify common fonts that people have on their computer that look more like BrownBold.
It's a real pain the FF often chokes on FontSquirrel fonts. We get a lot of threads here about that.