Are there specific Conditional Comments available for older versions of Firefox? (eg 3.0)
No, they are only supported by IE.
There are CSS hacks though. See: http://perishablepress.com/press/2009/06/28/css-hacks-for-different-versions-of-firefox/
Not to my knowledge. As far as I know, conditional comments are an Internet Explorer-only feature.
I am trying to create a solid fallback for @font-face by initiating Cufón for older browsers. Conditional comments came to mind but perhaps there is another route?
You just have to inject the cufón script tags conditionally.
Received an email from Faruk Ates the developer of [Modernizr][1]
[1]: http://www.modernizr.com/ confirming that it will do the trick.... and more:-)
来源：https://stackoverflow.com/questions/3041870/conditional-comments-firefox