404. That’s an error.

The requested URL /bookmarks/mark?op=edit&bkmk=http%3A%2F%2Fdata.bnf.fr%2Ffr%2F16552949%2Fcecile_nerot%2F&title=C%C3%A9cile+N%C3%A9rot was not found on this server. That’s all we know.