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In terms of Hypertext Transfer Protocol errors, ‘404’ is the numeric status code returned to the client when the server is unable to find what was requested. It is accompanied by the textual reason phrase ‘File Not Found’.

However, ‘404’ and ‘[Noun] Not Found’ are being used in contexts other than that of server and client communications. ‘404’ has become synonymous with ‘absent’, ‘astray’, and even ‘clueless’.

It has become common practice for developers to create custom ‘404 File Not Found’ pages which display instead of the browser’s default ‘404 File Not Found’ page.

Some webpages imitate ‘404 File Not Found’ pages, often for humor and parody.

Similarly infamous numeric status codes can be found in the ‘4xx’ series, which is reserved for errors made by the client such as ‘403 Forbidden’ and ‘401 Unauthorized’.


The 404 Research Lab offers the following account,

HTTP status codes were established by the World Wide Web Consortium (W3C) in 1992, as a part of the HTTP 0.9 spec. They were defined by Tim Berners-Lee, the same person who single-handedly invented the web and the first web browser in 1990.

The unreliable Room404 offers an unsubstantiated and likely fictitious history,

In an office on the fourth floor (room 404), they placed the World Wide Web’s central database: any request for a file was routed to that office, where two or three people would manually locate the requested files and transfer them, over the network, to the person who made that request.


When the database started to grow, and the people at CERN realised that they were able to retrieve documents other than their own research-papers, not only the number of requests grew, but also the number of requests that could not be fulfilled, usually because the person who requested a file typed in the wrong name for that file. Soon these faulty requests were answered with a standard message: ‘Room 404: file not found’.

The 404 Research Lab rejects this explanation with the following account,

Sorry to disappoint you all, but there is no Room 404 in CERN – it simply doesn’t exist, and certainly hasn’t been preserved as “the place where the web began”. In fact, there is a display about this, including a model of the first NeXT server, but the whole “Room 404” thing is just a myth.


Different browsers display different ‘404 File Not Found’ pages, unless the website is configured to display a custom webpage or if the client subscribed to a Domain Name Server which alters the browser’s actions. Perhaps the most notorious and recognizable ‘404 File Not Found’ page belongs to Internet Explorer 6.

Google Chrome 5.0

Firefox 3.6

Internet Explorer 8

Internet Explorer 6



‘404’ is used to refer to something that is ‘absent’ or ‘astray’. As these Quote Database results exemplify, ‘404’, sometimes accompanied by ‘[Noun] Not Found’, has found a presence both on and off the Internet to signify the absence of something.

arkan: You know, you really ought to have a bra with 403: forbidden on it.

Labyrinth: And you really ought to have a pair of boxers with 404: not found.

The British Broadcasting Corporation reports that ‘404’ also refers to ‘clueless’.

Web Development and Web Design

Rather than have the browser display its standard ‘404 File Not Found’ page, developers have resorted to creating a custom webpage. This has several advantages including,

  • Improved navigation.
  • Displaying advertisements.
  • Improved appearance.
  • Displaying creativity.

Many of these custom ‘404 File Not Found’ webpages creatively make use of graphics , animations , and music .

Listings of interesting ‘404 File Not Found’ webpages can be found on the 404 Research Lab and ‘lightecho’ and ‘sendcoffee’ .

4chan displays a random picture of its mascot, Yotsuba, when a ‘404 File Not Found’ error occurs, which resulted in the meme ‘404 girl’ .

A common phrase on 4chan is “in b4 404” or “in before 404” which means to enter a thread before the thread expires and is replaced with a 404 error.

xkcd has comics located at ‘http://www.xkcd.com/403/’ and ‘http://www.xkcd.com/405/’, but ‘http://www.xkcd.com/404/’ results in a ‘404 File Not Found’ error.

A blog called ‘the other side of the moonproposed that ‘404 File Not Found’ pages should display a listing of missing children and provided some PHP coding. Influenced by this, Scott Hanselman attempted to create a listing in HTML and Javascript. Demonstrations of this ‘404 File Not Found Page’ can be found here , here , here , and here .


Identical ‘404 File Not Found’ pages exist, often copying the appearance of the ‘404 File Not Found’ page of Internet Explorer 6 while changing the text. Some of these imitations refer to the ‘Last Page of the Internet’ . Some examples of these imitations include,

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