protected function checkAge()
    {
        $this->_is_old = false;

        switch ($this->_browser_name) {
            case 'Opera':
                if ($this->_version < 10)
                    $this->_is_old = true;
                break;
            case 'Firefox':
            case 'Iceweasel':
                if ($this->_version < 3)
                    $this->_is_old = true;
                break;
            case 'Safari':
                if ($this->_version < 5)
                    $this->_is_old = true;
                break;
            case 'Chrome':
                if (version_compare($this->_version, 5, '<'))
                    $this->_is_old = true;
                break;
            case 'iPhone':
            case 'iPod':
                $this->_is_old = true;
                break;
        }
    }