Understanding common HTTP errors

It is important to understand HTTP common errors. If you can tell them apart, then you will be able to control your Web server with a higher degree of accuracy and effectiveness. These are the codes that the Web server uses to communicate with the Web browser or user agent.

These messages include the standard 404 error message for a page not found as well as more obscure messages such as 101 Switching protocols. The codes can be divided into five subject areas: informational status codes, successful status codes, redirection status codes, client error status codes and server error status codes.

The following links explain the various error messages in more detail.

  • HTTP Status Codes 100-101 – Informational Status Codes: These messages just relay information. They do not belong to HTTP/1.0, so servers don’t respond to these messages. They are provisional responses and browsers may ignore them.
  • HTTP Status Codes 200-206 – Successful Status Codes: The status messages in the 200 series indicate that the request succeeded. In fact, 200 OK is the most common HTTP status message. This message means the server answered the request.
  • : As the name suggests, status messages in this series signals that the requested resource has changed locations.
  • HTTP Status Codes 400-416 – Client Error Status Codes: These messages mean that an error has occurred on the client or user agent’s end.
  • HTTP Status Codes 500-505 – Server Error Status Codes: In contrast to the messages above, status messages in this series signal a problem has occurred on the server’s end.


According to Google, below is a list of the five most common errors for you to study and understand.

1. HTTP error 500 (internal server error)

The description of this error pretty much says it all. It’s a general-purpose error message for when a web server encounters some form of internal error. For example, the web server could be overloaded and therefore unable to handle requests properly.

2. HTTP error 404 (not found)

A 404 error happens when you try to access a resource on a web server (usually a web page) that doesn’t exist. Some reasons for this happening can for example be a broken link, a mistyped URL. Or that the webmaster has moved the requested page somewhere else (or deleted it). To counter the ill effect of broken links, some websites set up custom pages for them (and some of those are really cool).

3. HTTP error 403 (forbidden)

This error is similar to the 401 error, but note the difference between unauthorized and forbidden. In this case no login opportunity was available. This can for example happen if you try to access a (forbidden) directory on a website.

4. HTTP error 400 (bad request)

This is basically an error message from the web server telling you that the application you are using (e.g. your web browser) accessed it incorrectly or that the request was somehow corrupted.

5. HTTP error 401 (unauthorized)

This error happens when a website visitor tries to access a restricted web page but isn’t authorized to do so, usually because of a failed login attempt.

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