Pop up window...How to centre?

I am putting a pop up window on a website and I can get the window to pop up correctly. However it opens top left as default and I want it centred. Any ideas? Also it comes up as untitled document? Anyone know how to fix this???

Heres the Javascript

<script language=“JavaScript”> function myFunction()
{ NewWindow=window.open(‘address’,‘newWin’,‘width=650,height=450,left=0 ,top=0,toolbar=No,location=No,scrollbars=No,status =No,resizable=No,fullscreen=No’); NewWindow.focus(); screen_height = window.screen.availHeight; screen_width = window.screen.availWidth; left_point = parseInt(screen_width/2)-(800/2); top_point = parseInt(screen_height/2)-(600/2); setTimeout('NewWindow.moveTo(left_point,top_point) ',100); void(0); } </script>