404 error

The 404 error is one of the standard response codes of the telnet protocol on which the web's HTTP is based. The first 4 indicates a client error such as a mistyped URL. The middle 0 refers to a general syntax error. The last 4 just indicates the specific error in the group of 40x, which in this case is "URL Not Found".

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Based on material from FOLDOC, used with permission. Update as needed.