see the script
in action
The window is open by (target="_blank") so its not pop up and cannot be blocked
by pop up blockers
(works on any monitor resolution)
<SCRIPT language=JavaScript>
<!--
self.focus();
self.resizeTo(400,400);
zleva=(screen.width-400)/2;
zhora=(screen.height-400)/2;
self.moveTo(zleva,zhora);
if (self != top) top.location = self.location
//-->
</SCRIPT>