The 404 Not Found error is an HTTP status code indicating that the server is unable to locate the requested resource. This error generally happens when a user attempts to reach a webpage or file that does not exist on the server. It can occur due to a mistyped URL, a file that has been moved or deleted, or a broken link on the website. For instance, if a visitor clicks on a link to an article that has been removed or relocated without a proper redirect, the server will display a 404 Not Found error. This error acts as an indication that the intended path does not lead to an existing webpage. Addressing and managing 404 errors is crucial for website upkeep and user satisfaction. Regularly repairing broken links, setting up redirects for moved content, and designing an informative 404 error page can enhance site navigation and retain user engagement even when they encounter an error.