Vedi se così va bene
<script language='javascript'>
var PopupWindow=null;
function Popup(mypage,myname,w,h,pos,infocus){
if(pos=='random'){
LeftPosition=(screen.width)?Math.floor(Math.random()*(screen.width-w)):100;
TopPosition=(screen.height)?Math.floor(Math.random()*((screen.height-h)-75)):100;}
if(pos=='center'){
LeftPosition=(screen.width)?(screen.width-w)/2:100;
TopPosition=(screen.height)?(screen.height-h)/2:100;}
else if((pos!='center' && pos!='random') || pos==null){LeftPosition=100;TopPosition=100;}settings='width='+ w + ',height='+ h + ',top=' + TopPosition + ',left=' + LeftPosition + ',location=no,directories=no,menubar=no,toolbar=no,status=no,scrollbars=yes,resizable=no,dependent=no';
PopupWindow=window.open('',myname,settings);
if(infocus=='front'){acePopupWindow.focus();acePopupWindow.location='http://tuapagina.com';}
}
//-->
</script>