General familiarity with error messages and application codes on websites

Error messages have a general category of common codes in hosting servers and browsers, these codes are divided into categories 100, 200, 300, 400 and 500, each category indicating specific errors that are generally described as is below:

  • Category 200 status codes are returned to valid browser requests.
  • 300 codes are for redirect types.
  • 400 codes are returned to errors that occurred during the request from the user side.
  • Category 500 codes refer to server-side errors.

As mentioned in the categories of codes, each one is expected to perform a specific operation, here we explain the most common codes.


The most common messages of category 200 on the website

200: Indicates a successful request and a file is returned in response.

201: This code refers to the successful response of creating a new resource on the server, like creating a file.


The most common messages of category 300 on the website

301: This code refers to a permanent redirect at the address. After this, other requests are directed to the redirected address instead of the original address. In other words, the requested content has been permanently transferred from the current address to the new address

302: This type of redirection means that the content is available at the desired address, but you will be temporarily redirected to another address.

304: This redirection is used for the cache mechanism of browsers. In each request to a web page, some information such as photos and some scripts are stored in the browser’s memory to save internet usage and load pages faster. In subsequent requests, the file’s saving date is compared with its version on the web server, and if the requested file does not expire, the server returns a 304 code and the saved file is displayed in the browser.


The most common 400 error messages on the website

The reason for displaying the 404 error

400: The address in the request to the server is not valid.

401: The requested address requires providing a username and password.

403: Access to the requested content is not permitted.

404: The requested file or page does not exist in the specified path.

410: The requested file or page has been deleted in the path announced by the site administrator.


The most common 500 error messages on the website

The reason for displaying the 503 error

500: It means the occurrence of an internal error in the server, which usually occurs when updating software or applying settings.

502: This error usually occurs when the Gateway between the server and the browser is unable to complete the request and response process, and the problem is usually resolved after several attempts from the user’s side.

503: The 503 Service Unavailable error is one of the famous http status codes, which means that the service is not available in the form of 503. Error 503 on the Internet means that the website server is currently unavailable, if the number of times and time of the 503 error increases, it is a bad consequence for the site’s SEO.

505: When the http protocol used by the browser is not supported on the server.


This article has been collected according to the most common observed messages, so for more information about errors and status messages, you can refer to the article List of HTTP status codes or to the English article List of HTTP status codes.

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