You did not tell it where to redirect to.
To do this add the action="" to the form
<html xmlns="http://www.w3.org/1999/xhtml">
<form action="youraspx.aspx" name="myform">
<table cellpadding="0" cellspacing="0" width="800px">
<tr>
<td><input type="image" value="Submit"></td>
</tr>
</table>
</form>
</html>
</html>
Oh and you should put a method also.
method="get or post"