$(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
原文：http://www.cnblogs.com/kojya/p/4262124.html