function check_email_form(form)
{
  if (form.name.value == "")
  {
    alert(mail_enter_your_name);
    form.name.focus();
    form.name.select()
    return (false);
  }

  if (form.address.value == "")
  {
    alert(mail_enter_address);
    form.address.focus();
    form.address.select()
    return (false);
  }

  if (isvalidemail(form.address) == false) {
    alert(mail_at_symbol);
    form.address.focus();
    form.address.select()
    return (false);
  }

  if (form.subject.value == "")
  {
    alert(mail_enter_subject);
    form.address.focus();
    form.address.select()
    return (false);
  }

  if (form.message.value == "")
  {
    alert(mail_enter_message);
    form.address.focus();
    form.address.select()
    return (false);
  }
}

function isvalidemail(thefield) {
	if (thefield.value.indexOf('@') == -1)
		return false;
	 else
		return true;
}