模拟弹出窗口效果，关闭层之前，不能选择后面的页内容

var bgObj=document.createElement("div"); 
        bgObj.setAttribute('id','bgDiv'); 
        bgObj.style.position="absolute"; 
        bgObj.style.top="0"; 
        bgObj.style.background="#cccccc"; 
        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); 
         
        var msgObj=document.createElement("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";

var title=document.createElement("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=function(){ 
            document.body.removeChild(bgObj); 
            document.getElementById("msgDiv").removeChild(title); 
            document.body.removeChild(msgObj); 
            } 
       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>
<input type="button" value="点击这里" onclick="sAlert('test弹窗效果');" />

[Ctrl+A 全选注:如需引入外部Js需刷新才能执行]