The code below will change the background-color of divs depending on what browser the user is viewing the web page under. Since * cascades down to IE7 and below, we use _ after that declaration so that IE6 (and below) has a different background color from IE7.

div {
  background-color: #999; /* all browsers */
  *background-color: #ccc; /* add a * before the property - IE7 and below */
  _background-color: #000; /* add a _ before the property - IE6 and below */
}