Most likely what he pointed out as error 404 on the negative for the user experience and the improvement of the research stimuli. And with that, there is no part of the life cycle of the web. In this article,
All About 404 Errors For SEO

Most likely what he pointed out as error 404 on the negative for the user experience and the improvement of the research stimuli. And with that, there is no part of the life cycle of the web. In this article,