RGBA on Internet Explorer 7+

Here is a handy trick using ms-filter to have transparent backgrounds on ie,
css3 you declare
WHITE COLOR RGBA
background-color: rgba(255,255,255, .5);

ON IE IS CALL ARGB (ALPHA AT THE BEGINNING)
WHITE COLOR AS ARGB
#FFFFFFFF

background: transparent; /* Feedback color */
background: rgba(red, green, blue, alpha); /* For modern browsers */

-ms-filter: "progid:DXImageTransform.Microsoft.gradient(GradientType=1, StartColorStr='#FFFFFFFF', EndColorStr='#FFFFFFFF')"; /* For IE8 */
filter: progid:DXImageTransform.Microsoft.Gradient(GradientType=1, StartColorStr='#FFFFFFFF', EndColorStr='#FFFFFFFF'); /* For IE6,IE7 */
zoom: 1!important; /* Trigger hasLayout */

THE ONLY THING THAT YOU NEED TO TRANSFORM IT'S THE RGBA COLOR TO ARGB AND THAT'S IT HERE A GOOD CALCULATOR TO DO THAT.