Access Policy Manager® (APM®) sends an error page to a web application when, for example, the application sends a request to a non-existent domain name or uses a URL that is blocked by the configuration. By default, the error page is a human-readable HTML page with HTTP status 200. This can lead to errors if the web application expects an error status or error notifications, but receives a normal reply. Instead, proxy servers can reply with HTTP status 503. Current browsers display the content of HTTP 503 replies to the user, if possible, and client code can recognize an abnormal situation.
To change the default behavior to reply with HTTP status code 503 for an APM-generated error page, you can configure an access profile or an access policy.