.ui-widget-overlay-main {
    background:url("/images/ui/ui-bg_flat_0_aaaaaa_40x100.png") repeat-x scroll 50% 50% #AAAAAA;
    opacity:0.3;
}
.ui-widget-overlay-main {
    height:100%;
    left:0;
    position:absolute;
    top:0;
    width:100%;
}