Response Codes

The HTTP status each page answers with. Errors and redirects decide whether search engines and AI crawlers can use a page at all.

Page answers with a 4xx client error: The page answers with a 4xx status such as 404 or 410, so search engines drop it from their index and visitors land on a dead end.
Page gives no server response: Requests for the page got no usable HTTP response, from a timeout, DNS failure or refused connection, so crawlers cannot read or index it.
Page keeps failing with a 5xx server error: The server kept failing with a 5xx error when the page was requested, so search engines and AI crawlers could not read it and may drop it.
Page redirects to another URL: The URL listed for this page redirects to a different page, so visitors and crawlers take an extra hop and the listed URL is not the one indexed.
Page returns 404 but has content: The page shows full content to visitors but answers with a 404 status, so search engines and AI crawlers treat it as a page that does not exist.