Do you know what has happened?
The client knocks on the server and asks for the page to be shown. The server wakes up, searches the page, and answers: "Sorry, chief, according to my notes we have no such page. Maybe it makes sense to try another address?" "Hmmm..." - says the client, I'll inform the user, all right. Maybe the user is confused.
Understood? If no, join our Manual testing + Internship course. We will explain one more time :)