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   IE6  IE7  FF

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 <style>  
    #test   
    {   
        width:300px;   
        height:300px;   
          
        background-color:blue;      /*firefox*/
        background-color:red9;      /*all ie*/
        background-color:yellow;    /*ie8*/
        +background-color:pink;        /*ie7*/
        _background-color:orange;       /*ie6*/
    }  
    :root #test { background-color:purple9; }  /*ie9*/
    @media all and (min-0px){ #test {background-color:black;} }  /*opera*/
    @media screen and (-webkit-min-device-pixel-ratio:0){ #test {background-color:gray;} }  /*chrome and safari*/
    </style>  

http://www.cnblogs.com/WuQiang/archive/2011/08/23/2150240.html