400. That’s an error.

Google cannot redirect you to http://worldcat.org/search?q=Proposta+di+alcune+correzioni+ed+aggiunte+al+Vocabolario+della+Crusca.+Volume+primo+[-+3.+Par.+2.]+vincenzo+monti 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.