http 常见状态码

X-Crawlera-ErrorResponse CodeError Messagebad_session_id400Incorrect session IDuser_session_limit400Session limit exceededbad_auth401Unauthorized mashape requestbad_auth407 too_many_conns429Too many connections*header_auth470Unauthorized Crawlera header 500Unexpected errornxdomain502Error looking up domaineconnrefused502Connection refusedeconnreset502Connection resetsocket_closed_remotely502Server closed socket connectionsend_failed502Send failednoslaves503No available proxiesslavebanned503Website crawl banserverbusy503Server busy: too many outstanding requeststimeout504Timeout from upstream servermsgtimeout504Timeout processing HTTP streamdomain_forbidden523Domain forbidden. Please contact [e-mail]_header540Bad header value for <some_header>