The different types of error responses your site might generate can be content managed in the subsite configuration.
Page Not Found Error
A user attempting to navigate to a page that does not exist will generate a 404 response. The framework will present them with a standard error page which uses the site's header and footer and displays the message:
404 - Page Not Found
The page you are looking for cannot be found.
This standard error page can be overridden by selecting an article using the "Page not found" article picker in the subsite configuration.
The framework still returns a 404 response to the user's browser, but the body content of the error page will be that of the chosen article. The article can use any template.
A logged in user attempting to view a page they do not have permission to see will generate a security denied error. The framework will present them with a standard error page which uses the site's header and footer and displays the message:
403 - Forbidden
You are not permitted to access this content.
This standard error page can be overridden by selecting an article using the "Security denied" article picker in the subsite configuration.
Note that this error is only presented to users who are logged in and attempting to navigate to secured content they do not have access to. Users who are not logged in would be redirected to the site's login article. If after logging in they do not have permission to see the secured content, they would then receive this error.
Resource Gone Error
The resource gone error occurs when a user follows a link to something that no longer exists, and the resource is likely to be missing permanently. This generates a 410 response. This is most likely to happen if a user attempts to access files, including secure file references, that have been removed or expired.
The framework will present the user with a standard error page that can be overridden by selecting an article using the "Resource gone" article picker in the subsite configuration.
The unknown error page is displayed should an error occur on the site which is too technical to detail to the user, or contains sensitive information. This acts as a final fail-safe message if something has gone badly wrong.
The page displays the message:
Sorry, an error has occurred
We will work to correct the problem as quickly as possible, and apologise for any inconvenience caused
When the unknown error occurs, an email is sent to the site administrator. This page cannot be content managed