400. That’s an error.

Google cannot redirect you to http://worldcat.org/search?q=L'Observateur+françois+à+Londres+ou+Lettres+sur+l'état+présent+l'Angleterre+...+relativement+à+ses+forces,+à+son+commerce+et+à+ses+moeurs because the request was invalid.

This might be because the link was created a long time ago. Try your search again on Google. That’s all we know.