crossbrowser CSS mask without Javascript

gistfile1.css

/* see http://ggendre.posterous.com/css-mask-without-javascript for details */
.mask {
	position:fixed !important;
	position:absolute; 
	left: 0; 
	top: 0;
	width:100%;
	height:100%;
	overflow: hidden; 
	padding:0 !important;
	padding:0 20px;/* pour IE6*/
	background-color:#FFFFFF;
	z-index: 900;
	filter: alpha(opacity=70);
	-moz-opacity:0.7;
	opacity: 0.7;
}