遮罩半透明

<!--

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<title>无标题文档</title>
<script type="text/javascript" src="http://blog.colorbird.com/mootools_demo/script/mootools.js"></script>
<script language="javascript">
function show(){
/*定义两个DIV showbg是遮盖层 showdiv是弹出窗口*/
var showbg = new Element("DIV");
var showdiv = new Element("DIV");
showbg.id = "showbg";
/*定位*/
showbg.injectAfter($('main'));
showdiv.injectInside($(showbg));

/*设定遮盖层属性 filter是IE识别的透明 moz是FF的透明*/
/*设定层属性 filter是IE识别的透明 moz是FF的透明*/
$('showbg').setStyles('background-color:#000;filter:alpha(opacity=40);-moz-opacity:0.4;position:absolute;top:0;left:0;z-index:1000');
/****************这部分为修改**************************/
var textindiv = "<a href=javascript:void(0) onclick=removeshow()>关闭</a>";
showdiv.setHTML(textindiv);
/******************************************************/
dosize();

window.addEvents({
  'resize': function(){dosize();},
  'scroll': function(){dosize();}
});

function dosize(){
   showdiv.setStyle('width','100px');
   showdiv.setStyle('background','#fff');
   showbg.style.width = window.getWidth() + "px";
   showbg.style.height = window.getScrollHeight() + "px";

   showbgsx = window.getWidth();
   showbgsy = window.getHeight();

   showdivx = $(showdiv).getCoordinates().width;
   showdivy = $(showdiv).getCoordinates().height;
   showdivt = window.getScrollTop();

   showdivtop = Math.floor((showbgsy - showdivy) / 2)+showdivt;
   showdivleft = Math.floor((showbgsx - showdivx) / 2)-18;
   showdiv.setStyles('background-color:#fff;position:absolute;top:'+showdivtop+'px;left:'+showdivleft+'px;z-index:1001');
  }

function removeshow(){
   $('showbg').remove();
}
}
</script>
</head>
<body>
<div id="" style="height:1000px">
<a href="javascript:void(0);" onclick="show()">登陆</a>

</div>
<a href="javascript:void(0);" onclick="show()">登陆</a>
</body>
</html>

-->

遮罩 半透明

遮罩半透明