codice:
<html>
<head>
<script>
function openPopUp(){
window.open('','miaPop','width=320,height=240');
}
</script>
<title>pagina invio file</title>
</head>
<body>
<form METHOD="Post" ENCTYPE="multipart/form-data" ACTION="http://www.sisty.it/public/outputFile.asp" target="miaPop" onsubmit="openPopUp();">
<p align="center"><font color="#CDD1FC"><font face="Verdana" size="1">
Inserisci file</font><font face="Verdana" size="2">:</font></font><font face="Verdana" size="2">
<input TYPE="file" NAME="blob" size="20">
<input name="Enter" type="submit" value="Allega ">
</font>>
</form>
</td>
</body>
</html>
Cosi dovrebbe funzionare.