Error 404, also known as "Page Not Found" error, occurs when a user tries to access a web page that does not exist or is no longer available on the server. When a web server receives a request from a user's browser for a specific page, it looks for the file on its server. If it cannot find the file or page requested, it returns a 404 error message to the user's browser, indicating that the server could not find the requested resource.

A 404 error can occur due to several reasons, including the following:

• The page has been deleted or moved to a different location.

• The URL is mistyped or contains an error

• The web server is down or unavailable.

When a user encounters a 404 error, it is important to check the URL and try again, making sure that it is typed correctly. If the error persists, it may indicate that the requested page is no longer available, and the user may need to search for the content they were looking for on a different page or website.