404 not found

404 - Your "invisible censor"...

https://en.wikipedia.org/wiki/List_of_HTTP_status_codes

https://en.wikipedia.org/wiki/HTTP_404
404 Error - historical "the invisible censor" (Thailand, Tunisia) or "potentially illegal"

Movies:
https://en.wikipedia.org/wiki/List_of_Mr._Robot_episodes#ep36

There are five classes defined by the standard:

1. 1xx informational response – the request was received, continuing process
2. 2xx successful – the request was successfully received, understood, and accepted
3. 3xx redirection – further action needs to be taken in order to complete the request
4. 4xx client error – the request contains bad syntax or cannot be fulfilled
5. 5xx server error – the server failed to fulfil an apparently valid request

Request methods = HTTP VERBS:

1. CONNECT
2. DELETE
3. GET
4. HEAD
5. OPTIONS
6. PATCH
7. POST
8. PUT
9. TRACE

The 404 error message may appear as follows:

1. "Error 404"
2. "404 not found"
3. "The requested URL was not found on the server."
4. "HTTP Error 404"
5. "Error 404: page not found"

This message is usually displayed in black on a blank page.

Remember that the 404 error page can be fully customized.