Ciao roby, si è un idcontatore l'ho tolto e mi da ancora l'errore.
Forse è meglio che posto anche il cod della form che richiama questo script:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title> Esempio 6.3 </title>
<LINK REL="stylesheet" TYPE="text/css" HREF="aspStyle.css">
</head>
<body>
<form action="addstudent.asp" method="post">
<TABLE>
<TR>
<TD><DIV CLASS="lsnFig">
<TABLE BORDER="1" BGCOLOR="#C0C0C0" BORDERCOLORLIGHT="#FFFFFF">
<TR>
<TD> <SPAN CLASS="frmTitle">Informazioni dello studente</SPAN></TD>
</TR>
<TR>
<TD>
<TABLE BORDER="0" CELLSPACING="1" CELLPADDING="1">
<TR>

<TD> <SPAN CLASS="frmLabel">ID dello studente:</SPAN> </TD>
<TD COLSPAN="2"></TD>
</TR>
<TR>
<TD>
<INPUT TYPE="text" SIZE="20" NAME="txtSID"></TD>
<TD COLSPAN="2"></TD>
</TR>
<TR>

<TD><SPAN CLASS="frmLabel">Nome</SPAN></TD>
<TD COLSPAN="2"> <SPAN CLASS="frmLabel">Cognome</SPAN></TD>
</TR>
<TR>
<TD>
<INPUT NAME="Nome" TYPE="text" id="txtNome" SIZE="20"></TD>
<TD COLSPAN="2">
<INPUT NAME="Cognome" TYPE="text" id="txtCognome" SIZE="20"></TD>
</TR>
<TR>

<TD><SPAN CLASS="frmLabel">Indirizzo</SPAN></TD>
</TR>
<TR>
<TD COLSPAN="3"><INPUT NAME="Indirizzo" TYPE="text" id="txtIndirizzo" SIZE="40"></TD>
</TR>
<TR>

<TD><SPAN CLASS="frmLabel">Città</SPAN></TD>
<TD><SPAN CLASS="frmLabel">Stato</SPAN></TD>
<TD><SPAN CLASS="frmLabel">CAP</SPAN></TD>
</TR>
<TR>
<TD><INPUT NAME="Citta" TYPE="text" id="txtCitta" SIZE="20"></TD>
<TD><INPUT NAME="Stato" TYPE="text" id="txtStato" SIZE="3"></TD>
<TD><INPUT NAME="Cap" TYPE="text" id="txtCap" SIZE="10"></TD>
</TR>
</TABLE>
</TD>
</TR>
<TR>
<TD>
<TABLE BORDER="0" WIDTH="100%" CELLSPACING="0" CELLPADDING="0">
<TR>
<TD WIDTH="50%" ALIGN="center">
<INPUT TYPE="submit" VALUE="Invia" NAME="Submit">
</TD>
<TD WIDTH="50%" ALIGN="center">
<INPUT TYPE="reset" VALUE="Cancella" NAME="Clear">
</TD>
</TR>
</TABLE>
</TD>
</TR>
</TABLE>
</TD>
</form>
</body>
</html>

grazie