function Validator(theForm)
{

  if (theForm.Name_surname.value == "")
  {
    alert("Please enter a value for the \"Name_surname\" field.");
    theForm.Name_surname.focus();
    return (false);
  }

  if (theForm.Tel.value == "")
  {
    alert("Please enter a value for the \"Tel\" field.");
    theForm.Tel.focus();
    return (false);
  }

  if (theForm.Email.value == "")
  {
    alert("Please enter a value for the \"Email\" field.");
    theForm.Email.focus();
    return (false);
  }

  if (theForm.Message.value == "")
  {
    alert("Please enter a value for the \"Message\" field.");
    theForm.Message.focus();
    return (false);
  }

  if (theForm.Message.value.length > 400)
  {
    alert("Please enter at most 400 characters in the \"Message\" field.");
    theForm.Message.focus();
    return (false);
  }
  return (true);
}