What does HTTP status 404 mean, and how can you peg it as a single word?

404 → "racer" (r·s·r).

404 Not Found means the server was reached fine but has no resource at the address you asked for — the Web's most famous error, born with HTTP at CERN in the early 1990s. (The oft-repeated tale that it's named after a "room 404" at CERN is a myth; the number simply follows the status-code scheme.) The leading digit marks the class of every HTTP code: 4xx means the client asked for something wrong, as opposed to a server-side fault. The digits 4·0·4 are the sounds /r/·/s/·/r/, which spell racer: picture a racer skidding off the edge of a missing page. Peg 404 → racer.