ho provato il seguente codice messo in due file che ho chiamato a.htm e b.htm.
L'ho testato su ie6, ns7, mozilla, firefox, netscape navigator 4.7 e funziona correttamente

a.htm:
codice:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<title>Documento senza titolo</title>
</head>

<body onLoad = "window.open('b.htm')">
<h1>
 
A
</h1>
</body>
</html>
b.htm:
codice:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<title>Documento senza titolo</title>
</head>

<body>
<h1>
  <script language="javascript" type="text/javascript">
window.opener.close()
  </script> 
b
</h1>
</body>
</html>