function validate(form) {
var reason = "";

  reason += validate(form.firstname);
  reason += validate(form.surname);
  reason += validate(form.email);
  reason += validate(form.address);
  reason += validate(form.contactno);
      
  if (reason != "") {
    alert("Some fields need correction:\n" + reason);
    return false;
  }

  return true;
}

</script>