When you could use: nofollow is commonly used together with noindex after you’re trying to prevent a web page from getting indexed in addition to avoid the crawler from adhering to backlinks around the web page. The URL is returning a "not located" error (4XX) or server error (5XX) – https://medium.com/@w3moz/seo-search-engine-optimization-the-ultimate-guide-to-ranking-higher-e565f16d1362