兼容各浏览器的遮罩层css代码

css代码：
.div-dialog-mask{
	background: #000000;
    opacity: 0.7;/*非IE滤镜*/
	filter:alpha(opacity=70);/*IE滤镜*/
	z-index:1987; 
	position: fixed; /*虽然IE6不支持fixed，这里依然可以兼容ie6*/
	left: 0px; 
	top: 0px; 
	width: 100%; 
	height: 100%; 
	overflow: hidden;
}
/*ie6 遮罩select*/
.div-dialog-mask iframe{
	width:100%;
	height:100%;
	position:absolute;
	top:0;
	left:0;
	z-index:-1;
	filter:alpha(opacity=0);
	opacity: 0.7;
}

html代码：
<div class="div-dialog-mask" id="divMask">
    <iframe src="about:blank"></iframe>
</div>