HTTP Status Codes Reference

HTTP status codes are three-digit numbers returned by a server to indicate the result of an HTTP request. The first digit indicates the class: 1xx informational, 2xx success, 3xx redirect, 4xx client error, 5xx server error.

404 Not Found means the server cannot find the requested resource. It's the most well-known client error code.

301 is a permanent redirect — search engines update their index to the new URL. 302 is a temporary redirect — search engines keep the original URL in their index.

500 Internal Server Error means the server encountered an unexpected condition. It's a generic error indicating something went wrong on the server side.