alret只弹出一次

代码是
 <script language=javascript>
function getCookie(name) {
var cookiefound=false
var start=0
var end=0
var cookiestring=document.cookie;
var i=0;
while (i<=cookiestring.length)
{
start=i
end=start+name.length
if (cookiestring.substring(start,end)==name)
{cookiefound=true;
break;
}
i++;
}
if (cookiefound==true)
{
start=end+1;
end=cookiestring.indexOf(";",start);
if (end<start)
{
end=cookiestring.length;}
return cookiestring.substring(start,end);
}
return "";
}

function newcookie(id,value,guoqi)
{
var expires=new Date()
expires.setTime(expires.getTime()+24*60*60*30*1000) //30为天数，可改为任意数字
var expiryDate=expires.toGMTString();
document.cookie=id+"="+value+";expires="+expiryDate
}

if (getCookie("Alerted")=="") {
alert("弹出了")
newcookie("Alerted","yes")
}
else
{}
</script>