document.frmPageForm.onkeypress = KeyDownHandler;

function KeyDownHandler(e)
    {
        if(e == null)
        {
          e = event;
        }
        // process only the Enter key
        if (e.keyCode == 13)
        {
            // cancel the default submit
            e.returnValue=false;
            e.cancel = false;
            if(e.stopPropogation != null)
            {
              e.stopPropogation();
            }
            if(e.preventDefault != null)
            {
              e.preventDefault();
            }
            alert("You cannot press enter to submit form. You must click the button you wish to press.");
        }
    }