def assert_no_404_errors(self, multithreaded=True):
        """ Assert no 404 errors from page links obtained from:
            "a"->"href", "img"->"src", "link"->"href", and "script"->"src". """
        links = self.get_unique_links()
        if multithreaded:
            from multiprocessing.dummy import Pool as ThreadPool
            pool = ThreadPool(10)
            pool.map(self.assert_link_status_code_is_not_404, links)
            pool.close()
            pool.join()
        else:
            for link in links:
                self.assert_link_status_code_is_not_404(link)