弹出一个对话框后，使后面变成灰色
<html>
<head>
<title></title>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<style type="text/css">
* {
margin: 0;
padding: 0;
}
</style>
</head>
<body>
<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>
<p>测试</p>
<input type="button" value="点击这里" onclick="sAlert('测试效果嗯！效果还不错！ ');" />
<script type="text/javascript" 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;//浏览器工作区域内页面宽度
sHeight = screen.height;//屏幕高度（垂直分辨率）
//背景层（大小与窗口有效区域相同，即当弹出对话框时，背景显示为放射状透明灰色）
var bgObj = document.createElement("div");//创建一个div对象（背景层）
//定义div属性，即相当于
// <div id="bgDiv" style="position:absolute; top:0; background-color:#777; filter:progid:DXImagesTransform.Microsoft.Alpha(style=3,opacity=25,finishOpacity=75); opacity:0.6; left:0; width:918px; height:768px; z-index:10000;"> </div>
bgObj.setAttribute("id", "bgDiv");
//alert("***********")
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);//在body内添加该div对象
var msgObj = document.createElement("div")//创建一个div对象（提示框层）
//定义div属性，即相当于
// <div id="msgDiv" align="center" style="background-color:white; border:1px solid #336699; position:absolute; left:50%; top:50%; font:12px/1.6em Verdana,Geneva,Arial,Helvetica,sans-serif; margin-left:-225px; margin-top:npx; width:400px; height:100px; text-align:center; line-height:25px; z-index:100001;"> </div>
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";
//alert("***********")
var title = document.createElement("h4");//创建一个h4对象（提示框标题栏）
//定义h4的属性，即相当于
// <h4 id="msgTitle" align="right" style="margin:0; padding:3px; background-color:#336699; filter:progid:DXImageTransform.Microsoft.Alpha(startX=20, startY=20, finishX=100, finishY=100,style=1,opacity=75,finishOpacity=100); opacity:0.75; border:1px solid #336699; height:18px; font:12px Verdana,Geneva,Arial,Helvetica,sans-serif; color:white; cursor:pointer;" onclick=""> 关闭 </h4>
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 = removeObj;
var button = document.createElement("input");//创建一个input对象（提示框按钮）
//定义input的属性，即相当于
// <input type="button" align="center" style="width:100px; align:center; margin-left:250px; margin-bottom:10px;" value="关闭">
button.setAttribute("type", "button");
button.setAttribute("value", "关闭");
button.style.width = "60px";
button.style.align = "center";
button.style.marginLeft = "250px";
button.style.marginBottom = "10px";
button.style.background = bordercolor;
button.style.border = "1px solid " + bordercolor;
button.style.color = "white";
button.onclick = removeObj;
function removeObj() {//点击标题栏触发的事件
document.body.removeChild(bgObj);//删除背景层Div
document.getElementById("msgDiv").removeChild(title);//删除提示框的标题栏
document.body.removeChild(msgObj);//删除提示框层
}
document.body.appendChild(msgObj);//在body内添加提示框div对象msgObj
document.getElementById("msgDiv").appendChild(title);//在提示框div中添加标题栏对象title
var txt = document.createElement("p");//创建一个p对象（提示框提示信息）
//定义p的属性，即相当于
// <p style="margin:1em 0;" id="msgTxt"> 测试效果 </p>
txt.style.margin = "1em 0"
txt.setAttribute("id", "msgTxt");
txt.innerHTML = str;//来源于函数调用时的参数值
document.getElementById("msgDiv").appendChild(txt);//在提示框div中添加提示信息对象txt
document.getElementById("msgDiv").appendChild(button);//在提示框div中添加按钮对象button
}
</script>
</body>
</html>
