Let's say you are reading a free manual online and every page is stored as a different webpage with a common URL and only the last number changing (E.G. page 1

Let's say you are reading a free manual online and every page is stored as a different webpage with a common URL and only the last number changing (E.G. page 1 is book/1 page 2 is book/2 and so on). The only way to go to a certain page is with a "next page" link from the previous one. You read the index at page 1 and see that you cant find the information you need but page 500 is missing, a printing error in the index perhaps. Instead of clicking 499 times on the page links to see if the information you need is on page 500 you simply change book/1 to book/500. OH NO, the link on page 499 brings you to page 501 and it's not in the index because page 500 contains the truth about aliens so now you read it and are going to prison. That's in a nutshell what happened