It happens all the time. You’re looking for a web page. You suddenly encounter a “404: File Not Found” error. Which usually means that the page you were has moved or no longer exists. Perhaps you came to it through an old or incorrect link. Perhaps it was a typo. At any rate, where you are (the 404 page) isn’t where you wanted to be.
Try these pages and see if you can find what you were looking for: