404 error messages explained (File not found)

A 404 response means the site has no current page or file available at the requested URL — or, occasionally, does not want to reveal whether one exists — and it does not say whether that condition is temporary or permanent. It is a standard HTTP status code named 404 Not Found. Importantly, a 404 is almost never a problem with your computer or browser: the request got far enough to receive an answer; there is simply nothing (visible) at that address.

Why 404s happen

When your browser asks a server for a page, the answer carries a numeric status code. 200 means success, 301 means moved permanently, and 404 means nothing is available at the requested URL. Common causes:

• A mistyped URL — a stray character, wrong case, or missing part of the path. URL paths are generally case-sensitive, so treat /About and /about as different unless you know your platform normalizes them.
• A moved or renamed page whose old address is still linked somewhere.
• A deleted page that search engines or other sites still point to.
• A broken internal link on your own site.

A related code, 410 Gone, says the resource is no longer available and that state is expected to be permanent — the appropriate signal for content you know won't return, rather than a guaranteed way to get it de-indexed faster than a 404.

Turn your 404 into a helpful page

An unhelpful 404 is bleak: the visitor hits a dead end and often leaves. A good custom error page gives that visit a real chance of recovery. Make yours:

• Apologize plainly — the visitor shouldn't feel they did something wrong.
• Explain briefly that the page wasn't found, with a descriptive page title and main heading (that's an accessibility requirement, not decoration).
• Offer a way forward — links to popular pages, a clear link home, and a search box if your site search actually works well; every control keyboard-usable, the search field properly labeled.
• Match your site's look so it feels intentional, not broken — but keep technical details (paths, stack traces) private, and never echo the requested URL into the page unescaped.
• Still return a real 404 response status. A pretty page that returns 200 (a "soft 404") wastes crawling, can be excluded from search anyway, and muddies your indexing reports.

On Apache you point to your custom page in .htaccess — this needs the host to allow ErrorDocument there, and if the page is a script, verify the final response still carries status 404:

ErrorDocument 404 /404.php

(A historical note: very old versions of Internet Explorer ignored custom error pages smaller than 512 bytes. That quirk is long gone, but keeping your error page reasonably substantial is still good practice.)

A 404 is normal and unavoidable. Handle it well and a dead end becomes a helpful signpost back into your site.

What to do

1. Create a branded 404 page with a brief explanation, useful links, a home link — and a search box if your search earns it.
2. Register it with ErrorDocument 404 (or your platform's equivalent) and confirm the public URL returns a genuine 404 — testing through any CDN or proxy, and remembering a 404 can be cached briefly even after you fix the URL.
3. Check your available logs (server, application, CDN) for the URLs actually producing 404s — with access restricted and retention limited, since logs contain personal data like IP addresses.
4. 301-redirect a moved page to its closest equivalent so visitors land right and search engines can consolidate signals — and only when a close replacement exists; redirecting everything to the homepage frustrates people and can itself count as a soft 404.
5. Use 410 Gone for content you know is permanently gone; otherwise a plain 404 is the honest answer.