Transparent background for older browsers

The following css should support Firefox, Safari, Opera, Chrome, IE 7 +.

.rgba { 
   background-color: transparent; 
   background-color: rgba(200,200,200,0.8); 
   filter:progid:DXImageTransform.Microsoft.gradient(startColorstr=#99dddddd,endColorstr=#99dddddd);
   -ms-filter: "progid:DXImageTransform.Microsoft.gradient(startColorstr=#99dddddd,endColorstr=#99dddddd)";
}