The True Identity of "404"
If you've used the internet, you've surely encountered "404 Not Found" when trying to access a website. You understand the page wasn't found, but why such an odd number as "404"?
In fact, 404 is one of the HTTP status codes. These are 3-digit numbers that web servers use to communicate "the result of a request" to browsers, and the first digit follows a specific pattern.
- 1xx: Processing ("Got it, hold on a moment")
- 2xx: Success (200 OK is the classic. "Everything went well")
- 3xx: Redirect ("It's moved to a different location")
- 4xx: Client error ("There's a problem with your request")
- 5xx: Server error ("Sorry, it's our fault")
404 falls under "4xx = your side's problem," where "04 = not found." In other words, it means "the page at the URL you specified doesn't exist on this server." These status codes are part of the HTTP/HTTPS protocol that governs all web communication.
Is the "CERN Room 404" Legend True?
There's a famous internet urban legend that "404 originated from Room 404 at CERN (the European Organization for Nuclear Research), where the server was located." The story goes that Tim Berners-Lee, the inventor of the Web, worked in Room 404 at CERN, and when a file couldn't be found, the response was "I checked Room 404, but it wasn't there."
However, this is not true. Whether Room 404 even exists in CERN's buildings has never been confirmed, and Tim Berners-Lee himself has denied this theory. The number 404 was determined as part of the systematic numbering of status codes during the development of the HTTP specification.
Creative Uses of 404 Pages
Many companies use their 404 pages as an opportunity to entertain users.
- GitHub: Displays a "Star Wars"-style parallax animation with the message "This is not the web page you are looking for"
- Pixar: Shows an illustration of "Sadness" from the movie "Inside Out" crying
- LEGO: Features an animation of LEGO minifigures repairing a broken page
- Bloomberg: Displays "Are you lost?" and provides links to market data
404 pages serve the important role of guiding users to the homepage or search function instead of letting them leave the site when they hit a dead end.
Other "Interesting" Status Codes
- 418 I'm a teapot: Defined in RFC 2324 as an April Fools' joke in 1998 for when "a teapot is asked to brew coffee." It's a joke, but it exists as an official RFC
- 451 Unavailable For Legal Reasons: A page that's inaccessible for legal reasons. The number was chosen in reference to Ray Bradbury's novel "Fahrenheit 451" (a dystopian novel about book burning)
- 503 Service Unavailable: The server is temporarily overloaded. Commonly seen when popular ticket sales begin
- 301 Moved Permanently: The page has permanently moved. Accessing the old URL automatically redirects to the new one
How to Reduce 404 Errors
For website operators, 404 errors can also negatively impact SEO. Search engines may judge sites with many 404s as "poorly maintained."
- Set up 301 redirects when pages are deleted or moved
- Regularly check internal links and fix broken ones
- Prepare a custom 404 page that guides users to the homepage or search
- Configure proper HTTP security headers to ensure that even error pages are served securely
On IP Check-san as well, accessing a non-existent page displays a custom 404 page with navigation back to the homepage.
Summary
404 was born from the systematic numbering of HTTP status codes and has nothing to do with CERN's Room 404. Next time you encounter a 404 page, take a moment to enjoy whatever creative design that site has prepared.