In the computing dictionary 404 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 also includes 400: Bad Request, 401: Unauthorized, etc.

Or if you prefer; in the English dictionary, a 404 is defined in slang as 'a stupid or ineffectual person'.

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