function checkMail(mail)
{
	var mail_pattern = new RegExp();
	mail_pattern=/^[0-9a-z._-]+@+[0-9a-z._-]+\.[a-z]{2,4}$/i;
	
	if (mail_pattern.test(mail))
	{
		return true;
	}
	else
	{
		alert ('Nieprawidłowy adres e-mail.');
		return false;
	}
}