public function removeTag($tag)
    {
        if (is_array($tag))
        {
            foreach ($tag as $t)
            {
                if (isset($this->allowed_tags[$t]))
                    unset($this->allowed_tags[$t]);
                $this->remove_tags[$t] = true;
            }
        }
        else
        {
            if (isset($this->allowed_tags[$tag]))
                unset($this->allowed_tags[$tag]);
            $this->remove_tags[$tag] = true;
        }
        return $this;
    }