The Error 404 Page not found is the error page displayed whenever someone asks for a page that’s simply not available on your site. The reason for this is that there may be a link on your site that was wrong or the page might have been recently removed from the site.
A 404 error is an HTTP status code that means that the page you were trying to reach on a website couldn't be found on their server. Technically, an Error 404 is a client-side error, implying that the error is your mistake, either because you typed the URL in wrong or the page has been moved or removed from the website and you should have known.