@namespace url(http://www.w3.org/1999/xhtml);

@-moz-document url-prefix(http://stackoverflow.com/questions/) {

   pre{ font-family: monospace !important;    } 
   code{ font-family: monospace !important;   }


/*** If you want to fall back some other way. **
   pre{ font-family: 'Bitstream Vera Sans Mono' !important; 
        font-size: 7pt !important;
   } 
   code{ font-family: 'Bitstream Vera Sans Mono' !important;
         font-size: 7pt !important;
   }
*/

}