Application pool

http://technet.microsoft.com/en-us/library/dd364312%28v=ws.10%29

http://www.cnblogs.com/awpatp/archive/2010/05/30/1747569.html

http://www.developer.com/net/asp/article.php/2245511/IIS-and-ASPNET-The-Application-Pool.htm

 http://hi.baidu.com/koko200147/item/086e61cfe623d03298b4980e

http://blog.sina.com.cn/s/blog_3fa7f1a6010168ia.html

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.

http://www.microsoft.com/technet/prodtechnol/WindowsServer2003/Library/IIS/67e39bd8-317e-4cf6-b675-6431d4425248.mspx?mfr=true