转载：http://blog.sina.com.cn/s/blog_610f47c50100ohe4.html
原理其实很简单：首先绘制弹出的自定义对话框，将其使用display:none隐藏，因为设置为none，其在页面中并不占用空间；
遮蔽罩使用一个div，然后将其宽高设置为整个显示窗口大小，配置其透明度，在将其z-index属性大于主页面的z-index的值，也就是遮蔽层在主页面上方，如此即可
事先隐藏一个div，在需要的时候调出显示既可。
<!--以下代码从网上多处学习整合而成，由于来源不一，并经过自行修改，请原谅未作注明-->
<script type="text/javascript">
var docEle = function()
{
return document.getElementByIdx_x(arguments[0]) || false;
} function openNewDiv(_id)
{
var m = "mask";
if (docEle(_id)) document.body.removeChild(docEle(_id));
if (docEle(m)) document.body.removeChild(docEle(m)); //mask遮罩层 var newMask = document.createElement_x("div");
newMask.id = m;
newMask.style.position = "absolute";
newMask.style.zIndex = "1";
_scrollWidth = Math.max(document.body.scrollWidth,document.documentElement.scrollWidth);
_scrollHeight =Math.max(document.body.scrollHeight,document.documentElement.scrollHeight);
newMask.style.width = _scrollWidth + "px";
newMask.style.height = _scrollHeight + "px";
newMask.style.top = "0px";
newMask.style.left = "0px";
newMask.style.background = "#33393C";
newMask.style.filter = "alpha(opacity=40)";
newMask.style.opacity = "0.40";
document.body.appendChild(newMask); //新弹出层 var newDiv = document.createElement_x("div");
newDiv.id = _id;
newDiv.style.position = "absolute";
newDiv.style.zIndex = "9999";
newDivWidth = 250;
newDivHeight = 200;
newDiv.style.width = newDivWidth + "px";
newDiv.style.height = newDivHeight + "px";
newDiv.style.top = (document.body.scrollTop + document.body.clientHeight/2 - newDivHeight/2) + "px";
newDiv.style.left = (document.body.scrollLeft + document.body.clientWidth/2 - newDivWidth/2) + "px";
newDiv.style.background = "#EFEFEF";
newDiv.style.border = "1px solid #860001";
newDiv.style.padding = "5px";
newDiv.innerHTML = document.getElementByIdx_x("HideDlg").innerHTML;
newDiv.innerHTML+= " "
document.body.appendChild(newDiv); //弹出层滚动居中 function newDivCenter()
{
newDiv.style.top = (document.body.scrollTop + document.body.clientHeight/2 - newDivHeight/2) + "px";
newDiv.style.left = (document.body.scrollLeft + document.body.clientWidth/2 - newDivWidth/2) + "px";
}
if(document.all)
{
window.attachEvent("onscroll",newDivCenter);
}
else
{
window.addEventListener('scroll',newDivCenter,false);
} //关闭新图层和mask遮罩层 var newA = document.createElement_x("a");
newA.href = "#";
newA.innerHTML = "Cancel";
newA.onclick = function()
{
if(document.all)
{
window.detachEvent("onscroll",newDivCenter);
}
else
{
window.removeEventListener('scroll',newDivCenter,false);
}
document.body.removeChild(docEle(_id));
document.body.removeChild(docEle(m));
return false;
}
newDiv.appendChild(newA);
} function closeDiv()
{
if(document.all)
{
window.detachEvent("onscroll",newDivCenter);
}
else
{
window.removeEventListener('scroll',newDivCenter,false);
}
document.body.removeChild(docEle(_id));
document.body.removeChild(docEle(m));
return false;
}
</script>
<!--img控件，点击触发-->
<div id="1" align="center" style="cursor:pointer">
<br>
<img src="1.png" alt="" style="width:123px;height:43px;" onclick="openNewDiv('newDiv');return false;"/>
</div>
<!--隐藏的div，随意修改-->
<div id="HideDlg" style="display:none;">
<input name="Btn" type="button" value="1" onclick="window.location.href='http://1.aspx'
</div>
优点：显示效果好，无边框，弹出后始终保持在屏幕中部，主页面变灰。
缺点：代码复杂。
注意：如果是在motherpage中添加，触发控件如果为<input img>的时候，可能会触发页面自刷屏导致页面跳转被自己覆盖