<style type="text/css">
html,body{height:100%;overflow:hidden;}
body,div,h2{margin:0;padding:0;}
body{font:12px/1.5 Tahoma;}
#overlay #win center{padding-top:10px;}
#overlay #win button{cursor:pointer;}
/*
opacity:不透明度;
*/
#overlay{position:absolute;top:0;left:0;100%;height:100%;background:#000;opacity:0.5;filter:alpha(opacity=50);display:none;}
#win{position:absolute;top:50%;left:50%;400px;height:200px;background:#fff;border:4px solid #4E85FA;margin:-102px 0 0 -202px;display:none;}
#win h2{font-size:12px;height:18px;text-align:right;background:#4E85FA;border-bottom:3px solid #4E85FA;padding:5px;cursor:move;}
#win h2 span{color:#4E85FA;cursor:pointer;background:#fff;border:1px solid #4E85FA;padding:0 2px;}
#win #urlcontent
{
margin:10px 20px 0px;
text-align:center;
font-size:12pt;
color:#03C;
}
#urlcontent a:hover{
text-decoration:underline;
}
</style>
<script>
window.onload = function ()
{
var oWin = document.getElementById("win");
var oLay = document.getElementById("overlay");
var oBtn = document.getElementsByTagName("button")[0];
var oClose = document.getElementById("close");
var oH2 = oWin.getElementsByTagName("h2")[0];
var bDrag = false;
var disX = disY = 0;
oBtn.onclick = function ()
{
oLay.style.display = "block";
oWin.style.display = "block"
};
oClose.onclick = function ()
{
oLay.style.display = "none";
oWin.style.display = "none"
};
oClose.onmousedown = function (event)
{
(event || window.event).cancelBubble = true;
};
oH2.onmousedown = function (event)
{
var event = event || window.event;
bDrag = true;
disX = event.clientX - oWin.offsetLeft;
disY = event.clientY - oWin.offsetTop;
this.setCapture && this.setCapture();
return false
};
document.onmousemove = function (event)
{
if (!bDrag) return;
var event = event || window.event;
var iL = event.clientX - disX;
var iT = event.clientY - disY;
var maxL = document.documentElement.clientWidth - oWin.offsetWidth;
var maxT = document.documentElement.clientHeight - oWin.offsetHeight;
iL = iL < 0 ? 0 : iL;
iL = iL > maxL ? maxL : iL;
iT = iT < 0 ? 0 : iT;
iT = iT > maxT ? maxT : iT;
oWin.style.marginTop = oWin.style.marginLeft = 0;
oWin.style.left = iL + "px";
oWin.style.top = iT + "px";
return false
};
document.onmouseup = window.onblur = oH2.onlosecapture = function ()
{
bDrag = false;
oH2.releaseCapture && oH2.releaseCapture();
};
};
</script>
<body>
<div id="overlay"></div>
<div id="win">
<h2>
<span id="close">×</span>
</h2>
<div id="urlcontent">
<a href="#" style=" text-decoration:none">下载</a>
</div>
</div>
<center><button>弹出层</button></center>
</body>