Status Codes
Status codes are part of the response that carries quite a bit of information. Status codes start with the numbers 1 to 5, and each have specific meaning:
- 1XX - Informational
- 2XX - Success
- 3XX - Redirection
- 4XX - Client Error
- 5XX - Server Error
The most common status codes are:
- 200 OK - Everything went great
- 404 Not Found - The URL you requested doesn't exist
- 401 Unauthorized - The Authorization header you included doesn't permit you to access the url you requested
A more comprehensive list may be found on wikipedia.