JS弹出窗口（背景是蒙版）

function alertWin(title, msg, w, h){
 var titleheight = "22px";//提示窗口标题高度
 var bordercolor = "#0051AA";//提示窗口的边框颜色
 var titlecolor = "#FFFFFF";//提示窗口的标题颜色
 var titlebgcolor = "#0051AA";//提示窗口的标题背景色
 var bgcolor = "#FFFFFF";//提示内容的背景色
 var iWidth = document.documentElement.clientWidth;
 var iHeight = document.documentElement.clientHeight;
 var bgObj = document.createElement("div");
 bgObj.style.cssText = "position:absolute;left:0px;top:0px;width:"+iWidth+"px;height:"+Math.max(document.body.clientHeight, iHeight)+"px;filter:Alpha(Opacity=30);opacity:0.3;background-color:#000000;z-index:101;";
 document.body.appendChild(bgObj);
 var msgObj=document.createElement("div");
 msgObj.style.cssText = "position:absolute;font:14px '宋体';top:"+(iHeight-h)/2+"px;left:"+(iWidth-w)/2+"px;width:"+w+"px;height:"+h+"px;text-align:center;border:1px solid "+bordercolor+";background-color:"+bgcolor+";padding:1px;line-height:22px;z-index:102;";
 document.body.appendChild(msgObj);
 var table = document.createElement("table");
 msgObj.appendChild(table);
 table.style.cssText = "margin:0px;border:0px;padding:0px;";
 table.cellSpacing = 0;
 var tr = table.insertRow(-1);
 var titleBar = tr.insertCell(-1);
 titleBar.style.cssText = "width:100%;height:"+titleheight+"px;text-align:left;padding:3px;margin:0px;font:bold 13px '宋体';color:"+titlecolor+";border:1px solid " + bordercolor + ";cursor:move;background-color:" + titlebgcolor;
 titleBar.style.paddingLeft = "10px";
 titleBar.innerHTML = title;
 var moveX = 0;
 var moveY = 0;
 var moveTop = 0;
 var moveLeft = 0;
 var moveable = false;
 var docMouseMoveEvent = document.onmousemove;
 var docMouseUpEvent = document.onmouseup;
 titleBar.onmousedown = function() {
  var evt = getEvent();
  moveable = true;
  moveX = evt.clientX;
  moveY = evt.clientY;
  moveTop = parseInt(msgObj.style.top);
  moveLeft = parseInt(msgObj.style.left);
  document.onmousemove = function() {
   if (moveable) {
    var evt = getEvent();
    var x = moveLeft + evt.clientX - moveX;
    var y = moveTop + evt.clientY - moveY;
    if ( x > 0 &&( x + w < iWidth) && y > 0 && (y + h < iHeight) ) {
     msgObj.style.left = x + "px";
     msgObj.style.top = y + "px";
    }
   } 
  };
  document.onmouseup = function () {
   if (moveable) {
    document.onmousemove = docMouseMoveEvent;
    document.onmouseup = docMouseUpEvent;
    moveable = false;
    moveX = 0;
    moveY = 0;
    moveTop = 0;
    moveLeft = 0;
   }
  };
 }
 var closeBtn = tr.insertCell(-1);
 //得到是从哪来的，关闭窗口后跳回。
 var path =document.getElementById("pathMsg").value;
 
 closeBtn.style.cssText = "cursor:pointer; padding:2px;background-color:" + titlebgcolor;
 closeBtn.innerHTML = "<span style='font-size:15px; color:"+titlecolor+";'>×</span>";
 closeBtn.onclick = function(){
  document.body.removeChild(bgObj);
  document.body.removeChild(msgObj);
  //关闭窗口后跳回。
  window.location.href =path;
 }
 var msgBox = table.insertRow(-1).insertCell(-1);
 msgBox.style.cssText = "font:14px '宋体';";
 msgBox.colSpan  = 2;
 msgBox.innerHTML = "<table>"
               + "<tr>"
               + "<td><img src='/imgs/cl_2.gif'></td>"
               + "<td style='text-align:left;'>"+msg+"</td>"
                  + "</tr>"
                  + "</table>";
    //获得事件Event对象，用于兼容IE和FireFox
    function getEvent() {
     return window.event || arguments.callee.caller.arguments[0];
    }
}