Thread:Project:Support desk/MediaWiki:Common.css 404 error/reply (3)

When a page in MediaWiki does not exist, it sends a  response, but the normal empty page (with links to create the article) are rendered as usual. The HTTP 404 response should prevent search engines from indexing those pages, and browsers and proxies from caching those pages.

If you get a custom server error message instead of the normal page, then your server is misconfigured. Disable or fix the custom errors directive of your web server.

If that's not the problem, then clarify why the 404 response is a problem for you.