nella pagina del login fai cosi:
codice:
<%
If Request.Form("user") = "admin" and Request.Form("psw") = "12345" then
%>
<script>
window.opener.location.href="index.asp"
self.location.href="tua_pagina.asp"
</script>
<%else%>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<title>prova</title>
</head>
<body>
Errore
</body>
</html>
<%end if%>
cosi non apri nuove pagine e il blocca popup non si attiva.