代码如下：
<!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>一个弹出层并锁屏效果</title>
</head>
<body>
<div>
<div>
<p>测试</p><p>测试</p><p>测试</p><p>测试</p><p>测试</p><p>测试</p><p>测试</p>
<p>测试</p><p>测试</p><p>测试</p><p>测试</p><p>测试</p><p>测试</p><p>测试</p>
<input type="button" value="点击这里" onClick="sAlert('测试弹出层并锁屏效果');" />
</div>
</div>
<script language="javascript">
function sAlert(str)
{
var msgw,msgh,bordercolor;
msgw=400;//提示窗口的宽度
msgh=100;//提示窗口的高度
titleheight=25 //提示窗口标题高度
bordercolor="#336699";//提示窗口的边框颜色
titlecolor="#99CCFF";//提示窗口的标题颜色
var sWidth,sHeight;
sWidth=document.body.offsetWidth;//获取窗口宽度
sHeight=screen.height;//获取屏幕高度
var bgObj=document.createElement("div");//关键在这里，原理：在body中创建一个div，并将其宽度与高度设置为覆盖整个窗体，如此一来就无法对其它窗口时行操作
bgObj.setAttribute('id','bgDiv');
bgObj.style.position="absolute";
bgObj.style.top="0";
bgObj.style.background="#777";
bgObj.style.filter="progid:DXImageTransform.Microsoft.Alpha(style=3,opacity=25,finishOpacity=75";
bgObj.style.opacity="0.6";
bgObj.style.left="0";
bgObj.style.width=sWidth + "px";
bgObj.style.height=sHeight + "px";
bgObj.style.zIndex = "10000";
document.body.appendChild(bgObj);//设置完此div后将其显示出来
var msgObj=document.createElement('div');//创建一个消息窗口
msgObj.setAttribute("id","msgDiv");
msgObj.setAttribute("align","center");
msgObj.style.background="white";
msgObj.style.border="1px solid " + bordercolor;
msgObj.style.position = "absolute";
msgObj.style.left = "50%";
msgObj.style.top = "50%";
msgObj.style.font="12px/1.6em Verdana, Geneva, Arial, Helvetica, sans-serif";
msgObj.style.marginLeft = "-225px" ;
msgObj.style.marginTop = -75+document.documentElement.scrollTop+"px";
msgObj.style.width = msgw+"px";
msgObj.style.height = msgh+"px";
msgObj.style.textAlign = "center";
msgObj.style.lineHeight ="25px";
msgObj.style.zIndex = "10001";
var title=document.createElement("h4"); //创建一个标题，以备放置在消息层
title.setAttribute("id","msgTitle");
title.setAttribute("align","right");
title.style.margin="0";
title.style.padding="3px";
title.style.background=bordercolor;
title.style.filter="progid:DXImageTransform.Microsoft.Alpha(startX=20, startY=20, finishX=100, finishY=100,style=1,opacity=75,finishOpacity=100);";
title.style.opacity="0.75";
title.style.border="1px solid " + bordercolor;
title.style.height="18px";
title.style.font="12px Verdana, Geneva, Arial, Helvetica, sans-serif";
title.style.color="white";
title.style.cursor="pointer";
title.innerHTML="关闭";
title.onclick=function()
{
document.body.removeChild(bgObj);//移除覆盖整个窗口的div层
document.getElementById("msgDiv").removeChild(title);//移除标题
document.body.removeChild(msgObj);//移除消息层
}
document.body.appendChild(msgObj);
document.getElementById("msgDiv").appendChild(title);
var txt=document.createElement("p");
txt.style.margin="1em 0"
txt.setAttribute("id","msgTxt");
txt.innerHTML=str;
document.getElementById("msgDiv").appendChild(txt);
}
</script>
</body>
</html>