Some properties in CSS are preceded by "*" or "_".

color{
         background-color: #CC00FF; /*All browsers will display it as purple*/
         background-color: #FF0000\9; /*IE6, IE7, IE8 will display red*/
         *background-color: #0066FF; /*IE6 and IE7 will turn blue*/
         _background-color: #009933; /*IE6 will turn green*/
}
body{

        background:red; /*For Firefox and other browsers;*/
        *background:blue !important; /*For IE7, IE7 can recognize both the * sign and important; */
        *background: green; /*Even IE6 can recognize the * number*/
}