IIS 7 includes advances in diagnosing and troubleshooting Web applications. IIS supports buffering trace events for a given request and saving these events to disk only if they fall into a user-configured error condition. IIS also captures real-time state information about application pools, worker processes, sites, application domains, and running requests.
You must enable trace logging before a trace log will be created for a failed request.
Overview of troubleshooting in IIS 7.
Define failure conditions for applications and configure which trace events to log on a per-URL basis.
Configure IIS log settings.
View a list of worker processes running on a server and view a list of currently executing requests for each worker process.