404 is an error code that appears on websites. It means that a link is broken or does not lead to a valid page on a website.
It's the thing all site owners hate to see on their website, which can mess up a user's online experience. A user can stumble
onto a 404 page in a variety of ways. Maybe they followed a link on the website itself that leads to a 404, or maybe they have
a bookmark that leads to a dead-end. Sometimes, 404 links can also appear on other websites or via search engines.
The first thing to realize is that there are other “numbers” related to the status of loading a webpage. For example, when you're loading a regular webpage, it's a “200 OK” request, which means it loaded without any problems.
Tim Berners-Lee, considered the father of the internet, established HTTP status codes during the World Wide Web Consortium (W3C) in 1992. These codes, which are still in use today, are formatted in three-digit numbers. A code that starts with “4” means a client error, which means that the user requested a page that they cannot access.
400 Bad Request: This normally pops up when there's an incorrect request made to the site.
401 Unauthorized / 403 Forbidden: These appear when the user does not have the necessary permissions to access a page.
404 Not Found: This shows up when the resource, or the page, does not seem to exist on the server.
408 Request Timeout: This appears when the server timed out or hit its maximum time to load a page before the request finishes.