JS遮罩层

<input id="Button1" type="button" value="点击弹出层" onclick="ShowDiv('MyDiv','fade')" />
<!--弹出层时背景层DIV-->
<div id="fade" class="black_overlay">
</div>
<div id="MyDiv" class="white_content">
<div style="text-align: right; cursor: default; height: 40px;">
<br />
<span style="font-size: 16px;" onclick="CloseDiv('MyDiv','fade')">关闭</span>
</div>
遮罩层。
</div>
<br />
<center>
层的遮罩效果</center>

<style type="text/css">
.black_overlay
{
display: none;
position: absolute;
top: 0%;
left: 0%;
width: 100%;
height: 100%;
background-color: black;
z-index: 1001;
-moz-opacity: 0.8;
opacity: .80;
filter: alpha(opacity=80);
}
.white_content
{
display: none;
position: absolute;
top: 10%;
left: 10%;
width: 80%;
height: 80%;
border: 16px solid lightblue;
background-color: white;
z-index: 1002;
overflow: auto;
}
.white_content_small
{
display: none;
position: absolute;
top: 20%;
left: 30%;
width: 40%;
height: 50%;
border: 16px solid lightblue;
background-color: white;
z-index: 1002;
overflow: auto;
}
</style>

<script type="text/javascript">
//弹出隐藏层
function ShowDiv(show_div, bg_div) {
document.getElementById(show_div).style.display = 'block';
document.getElementById(bg_div).style.display = 'block';
var bgdiv = document.getElementById(bg_div);
bgdiv.style.width = document.body.scrollWidth;
// bgdiv.style.height = $(document).height();
$("#" + bg_div).height($(document).height());
};
//关闭弹出层
function CloseDiv(show_div, bg_div) {
document.getElementById(show_div).style.display = 'none';
document.getElementById(bg_div).style.display = 'none';
};
</script>

<style type="text/css">
#white_content{
display: none;
position:fixed;
top:0%;
left:0%;
width: 100%;
background-color:black;
z-index: 1002;
opacity: .50;
overflow: auto;}

</style>

<script language="javascript">
function test(){
var div = document.getElementById('white_content');
div.style.display = "block";}
//$('html,body').animate({scrollTop: '0px'}, 100);}
window.onload=function(){
setTimeout("test()",2000);}//两秒钟弹出div

</script>

<script language="javascript">
function text(id){
var div = document.getElementById(id);
if(white.style.display=='block')
{
white.style.display='none';}
else{
white.style.display='block';}
}

</script>