404

"The typical trigger for an error 404 message is when website content has been removed or moved to another URL. There are also other reasons why an error message could appear. These include:

The URL or its content (such as files or images) was either deleted or moved (without adjusting any internal links accordingly) The URL was written incorrectly (during the creation process or a redesign), linked incorrectly, or typed into the browser incorrectly The server responsible for the website is not running or the connection is broken The requested domain name can’t be converted to an IP by the domain name system (DNS) The entered domain name doesn’t exist (anymore) Dead links are often left for long periods of time since operators have no idea that the linked content has been deleted or moved. Many websites still appear in the search engine results pages (SERPs) even though they aren’t available online anymore (or at least not at the specified URL). Other linked websites such as blogs, news portals, etc. are often not informed that the site has been removed or can now be found under a new URL. Many website operators don’t check their external links regularly and therefore a functioning link could easily become a dead one".

https://www.ionos.com/digitalguide/websites/website-creation/what-does-the-404-not-found-error-mean/