Web sites and Web applications depend on the availability of Internet Information Services (IIS) application pools. IIS application pools in turn depend on the Windows Process Activation Service (WAS). If WAS is not running or errors occur during the startup or shutdown of an application pool, Web sites and Web applications may not be available.
To resolve this problem, try restarting the Windows Process Activation service. Stopping the WAS service will also stop the World Wide Web Publishing Service (W3SVC) and any other services that depend on WAS. Thus, you may also have to start these other services.
To stop and restart WAS:
Open an elevated Command Prompt window. Click Start, point to All Programs, click Accessories, right-click Command Prompt, and then click Run as administrator.
At the command prompt, type net stop was /y.
At the command prompt, type net start was.
To restart W3SVC, from the command prompt, type net start w3svc. Also, start any other services that were stopped when WAS was shut down.