Ho sbagliato scusa, prova a mettere i tag form fuori da <td> o <tr>

<form action="vendita.asp" method="post">
<table border="0" cellpadding="0" cellspacing="0" width="106">
<tr>
<td width="67">

</td>
<td width="39">
</td>
</td>
</tr>
<tr height="5">
<td rowspan="3" valign="top" align="left" xpos="10"><input type="text" name="textfieldName" size="5"></td>
<td height="6"></td>
</tr>
<tr height="5">
<td height="14" valign="top"><spacer type="block" width="1" height="5"><input type="image" src="img/ok.gif" width="20" height="12" border="0" value="submit" alt="invia" name="invia"></td>
</tr>
<tr height="5">
<td height="8"></td>
</tr>
</table></form>

---

Non so se sia questo il problema... prova!