http://zzk.cnblogs.com/s?w=httpModule&p=2
http://www.cnblogs.com/stwyhm/archive/2006/08/09/471729.html
http://www.cnblogs.com/cyan/archive/2009/02/04/1383580.html
http://www.cnblogs.com/tangself/archive/2011/03/28/1998007.html
http://msdn.microsoft.com/zh-cn/asp.net