你可以建立一个ads.js,下面就是这个JS文件的代码.把这个文件调用要你需要弹出广告的网页即可

function openpopup(){
document.writeln("  <SCRIPT language=javascript>");
document.writeln("window.open('http://www.netbei.com')");
document.writeln("</script\>");
}

function get_cookie(Name) {
var search = Name + "="
var returnvalue = "";
if (documents.cookie.length > 0) {
offset = documents.cookie.indexOf(search)
if (offset != -1) {
offset += search.length
end = documents.cookie.indexOf(";", offset);
if (end == -1)
end = documents.cookie.length;
returnvalue=unescape(documents.cookie.substring(offset, end))
}
}
return returnvalue;
}

function helpor_net(){
if (get_cookie('popped')==''){
openpopup()
documents.cookie="popped=yes"
}
}
helpor_net()

红色部分换成你要弹出广告的URL.