Renaming a page, and deleting the old version. One fault has been one buried deep in the checkers game. As well as creating 404's it was causing me grief in the log files. Checkers game dropped. You shouldn't have been playing it anyway.
Sometime visitors try to second guess the name of a file.
Every page on the site has its full URL printed on it somewhere. Use the menus. Every page can be found from the menus. We have a large number of pages, and the site is structured into different directories. We try to keep the structure simple, and are working to simplify it again, please use it.