弹出窗口自动关闭

chanceAd=1;
var ns=(document.layers);
var ie=(document.all);
var w3=(document.getElementById && !ie);
adCount=0;
function initAd(){
        if(!ns && !ie && !w3) return;
        if(ie)                adDiv=eval('document.all.sponsorAdDiv.style');
        else if(ns)        adDiv=eval('document.layers["sponsorAdDiv"]');
        else if(w3)        adDiv=eval('document.getElementById("sponsorAdDiv").style');
        randAd=Math.ceil(Math.random()*chanceAd);
        if (ie||w3)
        adDiv.visibility="visible";
        else
        adDiv.visibility ="show";
        if(randAd==1) showAd();
}
function showAd(){
if(adCount<adTime*10){adCount+=1;
        if (ie){documentWidth  =document.body.offsetWidth/2+document.body.scrollLeft-20;
        documentHeight =document.body.offsetHeight/2+document.body.scrollTop-20;}
        else if (ns){documentWidth=window.innerWidth/2+window.pageXOffset-20;
        documentHeight=window.innerHeight/2+window.pageYOffset-20;}
        else if (w3){documentWidth=self.innerWidth/2+window.pageXOffset-20;
        documentHeight=self.innerHeight/2+window.pageYOffset-20;}
        adDiv.left=documentWidth-200;adDiv.top =documentHeight-200;
        setTimeout("showAd()",100);}else closeAd();
}
function closeAd(){
if (ie||w3)
adDiv.display="none";
else
adDiv.visibility ="hide";
}
onload=initAd;
</script>
<div id="sponsorAdDiv" style="visibility:hidden">
<table width="450" height="350" bgcolor="008000"><tr><td>
<table width="445" height="345" bgcolor="F0FFF0"><tr><td>
<center>我搜特效代码基地http://www.wosowoso.com/，将于5秒后自动关闭</center>
</td></tr></table></td></tr></table></div>