List of HTTP Status Codes

August 22, 2011

in Search Engine Optimisation

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Going through my list of Google Webmaster Tools errors for one of my projects, I found a “509” error which I’ve never seen before. So, onto the Google I went and had a bit of a search to find out what it was and decided to freshen up on my knowledge of ¬†HTTP status codes whilst I was there. The last time I studied the subject was in 2006 so you could say I was due for some revision.

There are around 60 HTTP status codes that all mean different things and are grouped into 5 types which I’ll cover today:

  1. Informational (1xx)
    • Indicates that the request was received and is a provisional response, consisting only of the status-line and optional headers, and is terminated by an empty line.
  2. Success (2xx)
    • Indicates the action requested by the client was received, understood, accepted and processed successfully.
  3. Redirection (3xx)
    • Indicates that further action needs to be taken by the user agent in order to fulfil the request. The action required may be carried out by the user agent without interaction from the user if and only if the method used in the second request is GET or HEAD. A¬†redirect should not be requested more than five times. If this occurs, the redirections usually indicate an infinite loop.
  4. Client Error (4xx)
    • The most common type of error codes. Also has the most individual status codes counting in at 28. Indicates an error whether temporary or permanent which should then be displayed to the user. The infamous “418” status code also falls under this category which means “I’m a teapot” (Hyper Text Coffee Pot Control Protocol) which was created as an April Fools joke in 1998.
  5. Server Error (5xx)
    • Indicate cases where the server is aware it has encountered an error and is incapable of performing the request.

Each of the above categories contain on average around 5-10 codes , and the most common types of HTTP status codes used in the SEO world are listed below:

  • 200 OK
    • Standard response for “everything worked as it should”.
  • 301 Permanent Redirect
  • 302 Temporary Redirect
  • 401 Unauthorised
    • When authentication is possible but has failed resulting in denied access
  • 403 Forbidden
    • Authentication is not possible and access is denied.
  • 404 Not Found
  • 410 Gone
    • The page or resource used to be there, but isn’t anymore and isn’t coming back.
  • 500 Internal Server Error
    • Given when there is no other suitable message. Typically occurs with infinite loops and incorrectly configured .HTACCESS / Apache setups.
  • 503 Service Unavailable
    • Server is unavailable either due to maintenance or it is overloaded.
  • 509 Bandwidth Limit Exceeded (haha! Got ya!)
    • This was the new one for me. Usually I get the ‘503’ error when a sites bandwidth is exceeded. Turns out, this error is only displayed in certain flavours of Apache running the bw/limited extension.

Whilst this post certainly isn’t anything ground breaking or “new” it has definitely helped me refresh my knowledge and the codes and has hopefully helped you learn something new or refresh as well! More information can be found here.

As always, I welcome comments and feedback. Have I missed anything from the “Most Common Codes” list? What’s your favourite code?!

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