Gary Illyes from Google posted on Google+ that he has observed many large sites lose massive amounts of their pages in the Google index for misuse of 403 status codes in situations where they should be opting for 503s.
“We've seen huge sites lose load of their pages from our index because they were serving them with a 403 status code instead of a 503.”
A 403 status code will quickly remove content from the search engine giant's index. A 403 means a forbidden code:
“The server understood the request, but is refusing to fulfill it. Authorization will not help and the request SHOULD NOT be repeated. If the request method was not HEAD and the server wishes to make public why the request has not been fulfilled, it SHOULD describe the reason for the refusal in the entity. If the server does not wish to make this information available to the client, the status code 404 (Not Found) can be used instead.”
Though a 503 status code is temporary rather than permanent and it usually does not stand for immediate removal from the Google index, it is a Service Unavailable code:
“The server is currently unable to handle the request due to a temporary overloading or maintenance of the server. The implication is that this is a temporary condition which will be alleviated after some delay. If known, the length of the delay MAY be indicated in a Retry-After header. If no Retry-After is given, the client SHOULD handle the response as it would for a 500 response.”
Users should therefore be careful about making errors regarding their server status code as this can seriously impact Google traffic. Unless they want to try the 418 status code, they should cease and desist from this.Misuse of 403 Status Codes Costs Sites Loads of Pages: Google!,