Secret

These categories are for internal development use ONLY. They are directly adjacent to the public categories but suffixed with $ to differentiate them.

If the $ is left off the end, the page will show in the category page list, making it seem like it is viewable by the public. However, due to content restrictions, all pages within the namespace used for internal documents is not viewable by anyone but admins. Feel free to test it. Users that are not logged in are blocked from viewing these pages and will receive a message instructing them to log in. However, only admin have accounts (you can thank the spam bots for that one!) so logging in is not possible.

These categories are publicly accessible because it is impossible to block access on a page-by-page basis, and besides, there isn't anything here that isn't in the public category list. These categories will be impossible to find unless someone views the full category list, but the category tree is much more conductive to finding things, so perhaps they'll use that instead.