0 usually means the server is gone entirely.

ftp 0 22
ftp 550 Requested action not taken. File unavailable (for example, file not found, or no access).5
http 0 363
http 200 OK93559
http 403 Forbidden13
http 404 Not Found167
http 410 Gone35
http 429 2
http 500 Internal Server Error4
http 503 Service Unavailable1
http 522 1
http 523 1

94173 links checked for 94173 prods (100.00%), 614 broken (0.65%)