CssHackie6,7,8的hack分別是什么

#test { 
 width:300px; 
 height:300px; 
 background-color:blue; /*firefox*/
 background-color:red\9; /*all ie*/
 background-color:yellow; /*ie8*/
 +background-color:pink; /*ie7*/
 _background-color:orange; /*ie6*/ } 
 :root #test { background-color:purple\9; } /*ie9*/
 @media all and (min-width:0px){ #test {background-color:black;} } /*opera*/
 @media screen and (-webkit-min-device-pixel-ratio:0){ #test {background-color:gray;} } /*chrome and safari*/