Solve IE6, IE7, Firefox compatible with the simplest CSS Hack

Write three lines of code to control an attribute , different from Firefox, Ie7,ie6:

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

Note: This code causes the background to be orange in Firefox, Green in IE7, and blue in IE6.
The reason is as follows, Firefox does not recognize *, so the following two sentences are not executed, directly execute the first sentence; IE7 three can be identified, but because of the second sentence important, so the second sentence code is executed, IE6 can not identify!imprtant, according to the latest principles, Then take the last sentence for granted.

Note: Another way:

    background:orange;     *Background:green;    _background:blue;

Firefox does not support * and _, so only the first sentence; IE7 does not support _, so the implementation of the second sentence; IE6 realizes the third sentence.