ASP.NET provides a welcome set of new diagnostic tools to Web application development. The shift from interpretation to compilation means that all the debugging facilities available for standard application development are now available for Web application development too. Page and application tracing provide comprehensive diagnostic output for any page in an application, and generating custom trace messages is a great way to track problems in an application. The installation of ASP.NET also includes a number of performance monitor counters that track virtually every aspect of an application. Finally, it is possible to specify custom error pages to display to users when things inadvertently go wrong.