When the client accesses a non-existent resource, and a servlet in which an exception occurred, the Web container returns an error status code. An error page corresponding to the error status code returned from the Web container is displayed in the client. In an application server, instead of the error pages displayed in the client, pages created by the user can be displayed in the client. This is called error page customization.

The methods to customize the error pages include: Customization with the <error-page> tag of web.xml specified in Servlet specifications and customization with the Web server functionality. You can also use the error page customization with the in-process HTTP server.

For details on the error page customization when the Web server functionality is used, see 4.8 Error page customization with the Web server integration functionality. For details on error page customization with the in-process HTTP server, see 5.15 Error page customization (In-process HTTP server).