400. That’s an error.

Google cannot redirect you to http://worldcat.org/search?q=Caroli+Linnæi+...+Species+plantarum.+Tom.1-6+[in+7+pt.+No+more+publ.+vol.5+after+pt.2.+sect.+1].+carl+linnaeus 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.