/* Solution for IE 7 and Firefox 
*/
#ModalBackFilter {
    position:fixed; 
    top:0px; 
    bottom:0px; 
    left:0px;
    right:0px;
    overflow:hidden; 
    padding:0; 
    margin:0; 
    background-color:#000; 
    filter:alpha(opacity=50); 
    opacity:0.5; 
    z-index:1000; 
}

#ModalMessage { 
    position:fixed; 
    top:50%; 
    left:50%;
    z-index:1001; 
}

/* IE 6 - Other attempts at a solution (more fun)
*/

body { height: 100%; }

#progressBackgroundFilter 
{
    position:absolute;
    height: expression(document.body.clientHeight + "px");
    width: expression(document.body.clientWidth + "px");
}
#processMessage { 
    position:absolute; 
    top: expression((document.body.clientHeight * .30) + "px")
}