vabè ho risolto così:
codice:
<script language="JavaScript">
function PopupCentrata() {
   var w = screen.width - 7;
   var h = screen.height;
   /*var l = Math.floor((screen.width-w)/2);
   var t = Math.floor((screen.height-h)/2);*/
      window.open("home.asp","home"," scrollbars=no width=" + w + ",height=" + h + ",top=0,left=0");
 }
 </script>
e poi in home reindirizzo a seconda della risoluzione
codice:
<script language="javascript"> 
<!-- 
var s_width =''; 
var s_height =''; 
s_width=screen.width 
s_height=screen.height 

if (s_width == "800"){ 
location.href="home800.asp"; 
} 

if (s_width == "1024"){ 
location.href="home1024.asp"; 
} 

if (s_width == "1280"){ 
location.href="home1280.asp"; 
} 
//--> 
</script>