404 (Page Not Found)

404 is an error message displayed when clicking a link that doesn't work. The technical definition is that the visitor managed to communicate with the server, but the server could not find the requested resource – a broken link.

Why are 404 errors important to manage?

404 errors affect both user experience and SEO. Search engines view sites with many broken links negatively. Solutions include custom 404 pages, link monitoring, and 301 redirects.