404. That’s an error.

The requested URL /books?op=add&sig=ACfU3U1_mr8DLxkrp6NDlPwRgONFUB-PqA&uid=17075598207816629880&id=BrTJNQAACAAJ&continue=http://books.google.it/books%3Fq%3Deditions:LCCN99199362%26id%3De_xPAAAAMAAJ%26source%3Dgbs_book_other_versions_r%26hl%3Dit was not found on this server. That’s all we know.