Google's John Mueller has responded to a question about Search Console and 404 error reporting, suggesting that repeated crawling of pages with a 404 status code is a positive signal. The 404 status codes, often referred to as an error code, often confuse site owners and SEOs for their meaning that something is broken and needs to be fixed. The official web standard definition of the 404 Status Code is that the requested page was not found. However, if a web page is permanently gone and never returning, 410 is the correct server message to send in response to requests for the missing page. Google has a long tradition of crawling 404 pages in case those were removed accidentally and have been restored.