Why does a page appear while HTTP reports 404?
The server may supply an HTML document as the 404 response body. A branded error page does not need a successful status; the body and status serve different purposes.
REFERENCE / FAQ
Questions from the field.
Short answers to recurring points of confusion.
Why do some static files return a different MIME type?
MIME mapping depends on the server configuration and filename extension. Check the actual Content-Type response and ensure the files are served from the intended root.
Does a correct HEAD response prove the page is healthy?
No. HEAD avoids transferring the body. Use a real GET to verify that the content is present and that its resource links resolve.
Is a longer cache lifetime always better?
No. Long caching benefits stable assets, but can delay the availability of corrections and cause stale information. Choose a lifetime based on the content lifecycle.
Can I learn the HTTP version from HTML?
No. Protocol negotiation occurs before the page representation is delivered. Inspect TLS ALPN and the client/server connection rather than relying on visible page content.