Introduction to CSS hack in different browsers

The CSS hack to distinguish different browsers:

Difference between IE6 and FF:
Backgroundrange;*blue; </span>

Difference between IE6 and IE7:
Background:green!important;blue; </span>

Difference between IE7 and FF:
Backgroundrange; *background:green;

Difference ff,ie7,ie6:
Backgroundrange;*background:green!important;*blue; </span>

Note: IE can recognize *; standard browsers (such as FF) do not recognize *;

IE6 can recognize *, but not!important,
IE7 can recognize *, can also identify!important;
FF does not recognize *, but can identify!important;
In addition, add one, underline "_",
IE6 support underscores, IE7 and Firefox do not support underscores.