【代码片段】遮罩层

$(function() {  
var h = $(document).height()+"px";  
var w = $(document).width()+"px";  
$('#t').css({ height:h,width:w});  
 });   
   
    
<div id="t" style="border:solid red 1px;filter:alpha(opacity=0.5);opacity:0.5;">  
111111  
</div>  

转自：http://username2.iteye.com/blog/1616270