Understanding Error Codes can help you to quickly diagnose issues as well as give you a better overall understanding about how web servers work together.
204 (No Content)
The server has received the request but there is no information to send back.
206 (Partial Content)
The requested file was only partially sent to the user. This is usually the result of exceeding bandwidth usage.
301 (Moved Permanently)
The requested page has been permanently moved to another location. This error is usually followed by a redirect.
302 (Moved Temporarily)
The requested page has been temporarily moved to a new location, but will be returning to it's existing location at some point. This error is usually followed by a redirect.
400 (Bad Request)
The address you are requesting to load is malformed, therefor the website was unable to understand the request.
The page you have tried to access cannot be loaded until you have logged in with a valid username and password.
The page or resource you are trying to reach is forbidden by the server.
404 (Not Found)
The page you were trying to reach was not found on the website's server.
408 (Request Timeout)
When the website you are connecting to has reached it's load time limit.
414 (Request-URL Too Large)
The requested URL is too long in length.
415 (Unsupported Media Type)
The requested file is not supported by the browser.
500 (Internal Server Error)
This is an extremely general code meaning that something has gone wrong internally with the website.
502 (Bad Gateway)
When one server has received an invalid response from another server. This error is the result of an issue between two servers on the Internet that aren't communicating correctly.
503 (Service Unavailable)
The website's server is not available due to a temporary overload or maintenance work.
504 (Gateway Timeout)
Similar to the 502 (Bad Gateway) error code this means that one web server did not receive a timely response from another web server.
Keep in mind
Because these error codes are not related to your browser all of these codes will remain the same in all modern internet browsers.