An HTTP status error means the target responded, but outside the expected status range for the check. The response is evidence of what the server, proxy or edge layer reported at that moment.
Client and access errors
401 means authentication is required. 403 means access was forbidden. 404 means the requested page was not found. 429 means the target or edge service rate-limited the request.
Server and gateway errors
500 indicates an application error. 502 indicates a bad response from an upstream service. 503 means the service is unavailable or in maintenance. 504 means a gateway timed out waiting for upstream.
What to do next
Check the target directly, review application and proxy logs, inspect recent deployments and review any Retry-After, Cloudflare or gateway evidence recorded by WebCheck.