Official Documentation sources:

Mozilla: HTTP response status codes - HTTP | MDN

Standard: RFC 9110 RFC 9110 - HTTP Semantics

Status/Error codes in the 100 Range:

Information. These indicate progress and no record of these will be stored in a log.

Status/Error codes in the 200 Range:

Successful responses. These indicate successful completion and no record of these will be stored in a log. Status code 200 is the most common.

Status/Error codes in the 300 Range:

Redirects. These mean that the request was received, but then forwarded to a new URL.

301 is for permanent changes. If this is returned the browser will cache this info and if you try the old one again, will automatically redirect and not try the old one for, potentially, forever.

302 is for temporary changes. If this is returned the browser will usually try it again the next time you use it. The browser might put some time limit on how often it will try the original value, but it shouldn't be very long.

307 is a more restrictive version of 302. The temporary redirect is an 'exact' redirect.

308 is a more restrictive version of 301. The permanent redirect is an 'exact' redirect.

Status/Error codes in the 400 Range:

400: The server is suggesting the client submitted something wrong.

401: The server requires authenticated access, and no authenticated access was provided.

403: Access forbidden. The server requires authenticated access, authenticated access was provided, but the requester is known to not be allowed access. But some servers won't return 403, they will instead return 404.

404: arguably the one code that 'everyone' knows. Whatever you asked for doesn't exist. Servers are allowed to send this one instead of 403.

414: URI too long. The line submitted was too long and the server refuses to even try.

418: I'm a teapot. Originally an April fool's joke. Maintained in the standard to avoid forward problems. It means the server refuses to brew coffee in a teapot.

429: Too many requests. The user has sent too many requests in a time period, so has been refused. Designed in part to minimize damage due to DDoS (Distributed Denial of Service) attacks.

Status/Error codes in the 500 Range:

These mean you reached the server, but something went wrong. Most of these will be recorded in a log file on the server. If you are an on-prem, you can as your IT department to see if they can find it in the log and determine the problem. If on SaaS, send the details to Support@MaintenanceConnection.ca