404. That’s an error.

The requested URL /bookmarks/mark?op=edit&bkmk=http%3A%2F%2Fdata.bnf.fr%2F16204690%2Ftraite_de_francfort___1871%2F&title=Trait%C3%A9+de+Francfort+%3A+1871 was not found on this server. That’s all we know.