Mozilla Firefox 3.0 is the best which I really love to work with. even I have seen that its supporting html5.0 and css3.0 and higher scripting lanagues. This will be futures come to true. I am sure Microsoft is really worried about things moving forward on mozilla organization.
Long waited thing which is now Firefox 3.0 is supporting is animated PNG ( Portable Network Graphics) . as png itself Open Source developement. and another developement is of animated PNG. but previous versions of FF and IE 7 doesn’t support this feature. Let have a look at this animation in FF3.0
In GIF we generally keep each and every pixel transparent transparent. but now png supports 24 bit color. with 8 bit alpha formatting. for backward compatibility browser which doesn’t support Animated PNG then this file shows only first frame.
For More Details https://developer.mozilla.org/en/Animated_PNG_graphics