forse perchè manca il codice "madre" del javascript... che va messo tra i tag <head> </head>
prova a fare cosi dentro allì'head metti

codice:
<SCRIPT LANGUAGE='JAVASCRIPT' TYPE='TEXT/JAVASCRIPT'>
<!--
var win=null;
function NewWindow(mypage,myname,w,h,pos,infocus){
if(pos=="random"){myleft=(screen.width)?Math.floor(Math.random()*(screen.width-w)):100;mytop=(screen.height)?Math.floor(Math.random()*((screen.height-h)-75)):100;}
if(pos=="center"){myleft=(screen.width)?(screen.width-w)/2:100;mytop=(screen.height)?(screen.height-h)/2:100;}
else if((pos!='center' && pos!="random") || pos==null){myleft=100;mytop=2}
settings="width=" + w + ",height=" + h + ",top=" + mytop + ",left=" + myleft + ",scrollbars=yes,location=no,directories=no,status=no,menubar=no,toolbar=no,resizable=yes";win=window.open(mypage,myname,settings);
win.focus();}
-->
</script>
e quando richiami il popup nellìa href metti...