301 moved permanently

302 found

303 not modified

400 bad request

401 unauthorized

403 forbidden

404 not found

500 internal server error

501 not implementedh

URLError >HTTPError

URLError: not linked the internal server: no web connection; remote url not exit; HTTPError

******************************************

import urllib.error
import urllib.request
try:
    urllib.request.urlopen("http://blog.cssdn.net")
except urllib.error.URLError as e:
    if hasattr(e,"code"):
        print(e.code)
        if hasattr(e,"reason"):
            print(e.reason)

web crawling(plus3) errors solution