En lille funktion som du nok kan bruge.
<HTML>
<HEAD>
<SCRIPT LANGUAGE="JavaScript">
function NewWindow(mypage, myname, w, h, scroll) {
var winl = (screen.width - w) / 2;
var wint = (screen.height - h) / 2;
winprops = 'height='+h+',width='+w+',top='+wint+',left='+winl+',scrollbars='+scroll+',resizable';
win = window.open(mypage, myname, winprops);
if (parseInt(navigator.appVersion) >= 4) {
win.window.focus();
}
}
</SCRIPT>
</HEAD>
<BODY>
<A href="
http://www.yahoo.com/" onclick="NewWindow(this.href,'name','400','400','yes');return false;">Popup Yahoo.com</A>
</BODY>
</HTML>