Fonts are not working in Firefox 3.0

Yes, it is true @lavisrap. Prior to Firefox 3.5, it did not support @font-face, which is the method that Google Webfonts–and many other font replacement tools–uses.

There is a good article by John Daggett covering this issue here: http://hacks.mozilla.org/2009/06/beautiful-fonts-with-font-face/

You will need to find a different replacement method like sIFR. Here is a good round up of your choices: http://www.smashingmagazine.com/2009/10/22/rich-typography-on-the-web-techniques-and-tools/