js代码:弹出层，带关闭按钮

 <script>
function sAlert(txt)
{
//var eSrc=(document.all)?window.event.srcElement:arguments[1];
var shield = document.createElement("DIV");
shield.id = "shield";
shield.style.position = "absolute";
shield.style.left = "0px";
shield.style.top = "0px";
shield.style.width = "100%";
shield.style.height = document.body.scrollHeight+"px";
shield.style.background = "#333";
shield.style.textAlign = "center";
shield.style.zIndex = "10000";
shield.style.filter = "alpha(opacity=0)";
shield.style.opacity = 0;
var alertFram = document.createElement("DIV");
alertFram.id="alertFram";
alertFram.style.position = "absolute";
alertFram.style.left = "50%";
alertFram.style.top = "50%";
alertFram.style.marginLeft = "-225px" ;
alertFram.style.marginTop = -75+document.documentElement.scrollTop+"px";
alertFram.style.width = "450px";
alertFram.style.height = "150px";
alertFram.style.background = "#ccc";
alertFram.style.textAlign = "center";
alertFram.style.lineHeight = "150px";
alertFram.style.zIndex = "10001";

strHtml = "<ul style=/"list-style:none;margin:0px;padding:0px;width:100%/">/n";
strHtml += " <li style=/"background:#DD828D;text-align:left;padding-left:20px;font-size:14px;font-weight:bold;height:25px;line-height:25px;border:1px solid #F9CADE;/">[提示]</li>/n";
strHtml += " <li style=/"background:#fff;text-align:center;font-size:12px;height:120px;line-height:120px;border-left:1px solid #F9CADE;border-right:1px solid #F9CADE;/">"+txt+"</li>/n";
strHtml += " <li style=/"background:#FDEEF4;text-align:center;font-weight:bold;height:25px;line-height:25px; border:1px solid #F9CADE;/"><input type=/"button/" value=/" 确 定 /" id=/"do_OK/" onclick=/"doOk()/" /></li>/n";
strHtml += "</ul>/n";
alertFram.innerHTML = strHtml;
document.body.appendChild(alertFram);
document.body.appendChild(shield);
this.setOpacity = function(obj,opacity){
if(opacity>=1)opacity=opacity/100;
try{ obj.style.opacity=opacity; }catch(e){}
try{
if(obj.filters.length>0&&obj.filters("alpha")){
obj.filters("alpha").opacity=opacity*150;
}else{
obj.style.filter="alpha(opacity=/""+(opacity*150)+"/")";
}
}catch(e){}
}
var c = 0;
this.doAlpha = function(){
if (++c > 20){clearInterval(ad);return 0;}
setOpacity(shield,c);
}
var ad = setInterval("doAlpha()",1);
this.doOk = function(){
document.body.removeChild(alertFram);
document.body.removeChild(shield);
document.body.onselectstart = function(){return true;}
document.body.oncontextmenu = function(){return true;}
}
document.getElementById("do_OK").focus();
document.body.onselectstart = function(){return false;}
document.body.oncontextmenu = function(){return false;}
}


</script>