Checking for installed fonts with @font-face and local()
Firefox 3.5 was released earlier today, and joins Safari in supporting the @font-face rule with OpenType and TrueType font families, allowing you to use a wider range of fonts in your designs (as long as they are correctly licensed, of course).
One slight drawback of the technique is the blank space that’s displayed as the new font is loaded into the browser; this is especially unnecessary for users who already have that font natively on their system.