div遮罩层实现实例代码

这个代码不是很完善，能实现基本的功能；

另外有个问题，就是divOpenWin层的定位问题：发现如果其属性设置成display:none，那么就无法获取到它的offsetWidth和offsetHeight值。

暂时想到的解决办法有两个：

1、就是把top值设置负的高点，效果类似隐藏吧

2、动态定义width和height，在js处理部分直接赋值，这样修改起来也方便很多

代码如下：

<title>www.aspxhome.com</title><style type="text/css">#divPageMask{background-color:#000000; filter:alpha(opacity=50);left:0px;position:absolute;top:0px;}#divOpenWin{background-color:#EEEEEE;position: absolute;left:0px;top:-300px;z-index:50; width:300px;height:150px}</style><div id="divPageMask"></div><div id="divOpenWin"><center><a href="javascript:Close();">关闭</a><div id="DivInfo">请认真阅读本发帖说明 (15 秒后自动关闭)</div></center></div><script language="javascript">function $(id){return document.getElementById(id);}function Open(){   sDisp(0);     $("divPageMask").style.display="block";   resizeMask();   window.onResize = resizeMask;   $("divOpenWin").style.display="block";}function Close(){   sDisp(1);   divPageMask.style.width = "0px";   divPageMask.style.height = "0px";   divOpenWin.style.top = "-300px";   window.onResize = null;}function resizeMask(){divPageMask.style.width = document.body.scrollWidth;divPageMask.style.height = document.body.scrollHeight>document.body.clientHeight?document.body.scrollHeight:document.body.clientHeight;divOpenWin.style.left = (document.body.offsetWidth - divOpenWin.offsetWidth) / 2;divOpenWin.style.top = (document.body.offsetHeight - divOpenWin.offsetHeight) / 2;}function sDisp(val){var dispalyType;   var dType=["hidden","visible"];   var obj=document.getElementsByTagName("select");   for (i=0;i<obj.length;i++)   {     obj[i].style.visibility=dType[val];   }}Open();var secs = 15;for(i=1;i<=secs;i++) {window.setTimeout("update(" + i + ")",  i*1000);}function update(num) {if(num == secs) {Close();}else {printnr = secs-num;$("DivInfo").innerHTML = "请认真阅读本发帖说明 (" + printnr +" 秒后自动关闭)";}}</script>