usa window.open

file test168a.html
codice:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

<html>
<head>
<title>Untitled</title>
</head>
<body>
<script language="JavaScript" type="text/javascript">
<!--
function apritiSesamo() {
 window.open("test168b.html", null, "height=225,width=400,menubar=no,location=no,resizable=no,status=no");
} // function apritiSesamo()
//-->
</script>
Clicca qui
</body>
</html>
file test168b.html
codice:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

<html>
<head>
<title>Untitled</title>
</head>
<body>
Sono sesamo !!!
</body>
</html>