Every time your browser requests a web page, the server responds with a three-digit HTTP status code. Most of the time, these happen silently. But when things break, you'll see a big error on your screen. Here is what those numbers actually mean.
The 2xx family: Success!
200 OK: The perfect response. The request worked, and the server delivered the data. You don't see this because the website simply loads.
The 3xx family: Redirection
301 Moved Permanently: The URL you requested has officially moved somewhere else. This is critical for SEO.
The 4xx family: Client Errors (Your fault)
These imply the server is fine, but the browser (or the user) messed up.
- 403 Forbidden: You don't have permission to view that page.
- 404 Not Found: The most famous error. You clicked a dead link or typed the URL wrong.
The 5xx family: Server Errors (Their fault)
These mean the website's server crashed or is misconfigured.
- 500 Internal Server Error: A generic 'something exploded on our end' message. Usually a code bug.
- 502 Bad Gateway: The server acting as a middleman received an invalid response from another server.