CSS distinguishes IE6,7,FF

IE6 can recognize *, but not!important,
IE7 can recognize *, can also identify!important;
FF does not recognize *, but can identify!important;


Background:green!important; Background:orange; *background:blue;

Add another, underline "_", IE6 support underline, IE7 and Firefox do not support underline.

So we can also distinguish FIREFOX,IE7,IE6:
Background:green!important; *background:orange; _background:blue;

Note: No matter what method, the order of writing is the Firefox written in front, IE7 written in the middle, IE6 written in the last side.

CSS distinguishes IE6,7,FF