Added a Page not found page. When you are signed in it shows your navigation, the address you asked for, the area the address is in with a link to that area and its Help article, and links to Search, Dashboard and Help. A page that looked for a record says which kind of record is not at the address, and when it was deleted if the page knows. Signed out, the page offers Log in, a Help search and the area's Help article, and sign-in returns to the address.
Added a page for a request that could not be completed, and one for when Magpie is not available, in place of a plain sentence.
A script that asks for JSON gets a JSON answer with the same status.
For operators: every error-level log record is emailed to ERROR_ALERT_EMAIL, one per distinct message every ten minutes.