A 404 page is the standard error message that is displayed when a web browser attempts to access a page that does not exist.
The 404 error is generated by the web server when it cannot find the requested file or document on the server. It can occur for a number of reasons, such as if the file has been moved or deleted, if there is a typo in the URL, or if the server has been misconfigured.
Most web browsers will display a custom 404 page when they encounter a 404 error. This page can be used to provide information about what went wrong and how to fix it. It can also be used to provide search results, menu links, or other helpful information.