Edit in JSFiddle

.csshack{
    background:blue;
    background:blue\9; /*all ie*/
    background:blue\0/; /*ie8-ie9*/
    background/*\**/: blue\9; /* ie7-ie8*/
    *background:blue;/* or #background: blue */ /*ie6-ie7*/    
    +background:blue; /*ie7*/
    _background:blue; /*ie6*/
}
:root .csshack{
    background:blue; /*大于等于ie9*/
}
/* IE9, IE10 */
@media screen and (min-width:0\0) {
    .csshack { color: red}
}
/* IE 10+ */
@media screen and (-ms-high-contrast: active), (-ms-high-contrast: none) {
   #veintiun { color: red; }
}
/* saf3+, chrome1+ */
@media screen and (-webkit-min-device-pixel-ratio:0) {
 #diez  { color: red  }
}

/* iPhone / mobile webkit */
@media screen and (max-device-width: 480px) {
 #veintiseis { color: red  }
}
/* Firefox only. 1+ */
#veinticuatro,  x:-moz-any-link  { color: red }

/* Firefox 3.0+ */
#veinticinco,  x:-moz-any-link, x:default  { color: red  }

/* FF 3.5+ */
body:not(:-moz-handler-blocked) #cuarenta { color: red; }