Picto thématique

Rule n° 216 - The server sends a customised 404 Not found error page

Mistakes are inevitable. Even checking your links every ten minutes, a user can still type indxe.html instead of index.html. The 404 page is one of the most important pages of your site. Some agencies will bring particular care. Do not forget, this is a sign of professionalism.

#Accessibility #Server and performance #Conception #Development


  • Inform users of the error encountered and of the server’s continuing operation.
  • Inform users that the problem isn't caused by their connectivity.


Modify the web server configuration to send the user to a customised page when the requested resource does not exist

If the main server configuration is not directly accessible and if the environment allows it, use a local configuration by directory. For example, the Apache environment authorises the creation of an .htaccess file containing directives relating to error handling: ErrorDocument 404 /mapage.html.


From any URL address of the site checked:

  • Modify the URL address to obtain a 404 error, for example, by adding a series of random characters at the end of the address such as: https://www.example.com/dbvdjb
  • Check that the page returned corresponds to a customised page, consistent with the rest of the site, and not to the 404 page sent by default by the server (Apache, IIS, Nginx);
  • In the case of using a CMS, the latter may lead you to believe that it does not return the 404 page by default, so you will have to perform the same check via the URL address of an image, CSS or JS file to definitively validate this best practice.

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