>IAC, after having verified a few things, it seems the onkeypress is not affected by the auto complete key press. I must have had a version that was outdated. So, that makes sense. The onkeypress at the HTML control is bound to the HTML control itself and not the auto complete which is driven by the browser.

I certainly could not see the behaviour. Down-arrowing to a listed item and hitting enter completed the text box but did not trigger the submit. Hitting Enter again submitted the form:

   <form id="form1" runat="server">
        <input id="Text1" type="text" onkeypress="return handleKeyPress(event)" /><br />
      <script type="text/javascript">
        function handleKeyPress(event)
        {
          // return event.keyCode != 13;
          return true;
        }
      </script>
      <input id="Submit1" type="submit" value="submit" />
    </form>