The HTTP 404, 404 Not Found, 404, 404 Error, Page Not Found, File Not Found, or Server Not Found error message is a Hypertext Transfer Protocol (HTTP) standard response code, in computer network communications, to indicate that the browser was able to communicate with a given server...

A 404 error is rarely a reason to celebrate. At the end of the day, the website's visitors have not Reload the page: It might be that the error 404 has appeared for the simple reason that the page did...

RFC 7231, секция 6.5.4: 404 Not Found. Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content. The compatibility table in this page is generated from structured data.

Error 404 Not Found doesn't have any inherent negative impact on SEO. Additionally, if a permalink issue is causing sitewide 404 errors, Google won't be able to crawl any of your site's content.