CSS Background Transparency

/**
 *
 *    Background Transparency
 *
 *    Firefox 3
 *    Safari 2
 *    Opera 10
 *    IE5.5, IE6, IE7, IE8
 *
 *    IE hexadecimal filter value!
 *    Take our desired alpha level, 0.6, and multiply it with 255,
 *    then convert the result into hex. The first 2 numbers is the
 *    opacity level.
 *
**/
.alpha60 {

    /* Fallback for browsers without RGBa support */
    background: rgb( 0, 0, 0 );

    /* RGBa with 0.6 opacity */
    background: rgba( 0, 0, 0, 0.6 );

    /* IE5.5 -> IE7 */
    filter:progid:DXImageTransform.Microsoft.gradient(startColorstr=#99000000, endColorstr=#99000000);

    /* IE8 */
    -ms-filter: "progid:DXImageTransform.Microsoft.gradient(startColorstr=#99000000, endColorstr=#99000000)";

}