Ho provato a modificare la pagina dell'iFrame così:
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=windows-1252">
<title>Nuova pagina 1</title>
</head>
<body topmargin="0" leftmargin="0" rightmargin="0" bottommargin="0" marginwidth="0" marginheight="0">
<form name="selecter5" method="POST">
<input type="text" name="Dato3" size="20">
</form>
</body>
</html>
E' FUNZIONA
