TL;DR: Web servers can soon say “Error 451” — like “Error 404” that indicates censorship

TL;DR: A new response for web servers is “451” — like Error 404, but indicating censorship — is on track to official approval.

the 403 status code says “Forbidden”, but it doesn’t say “I can’t show you that for legal reasons.” Hence, 451 (which is also a great tip of the hat to Ray Bradbury).

Source: mnot’s blog: Why 451?