HTTPHandler

http://support.microsoft.com/kb/324066

http://www.codeproject.com/Articles/16384/Using-ASP-NET-HTTP-Modules-to-restrict-access-by-I

http://msdn.microsoft.com/en-us/library/ms228090%28v=vs.100%29.aspx

http://blog.csdn.net/zhaili1978/article/details/6335595

http://www.cnblogs.com/rrooyy/archive/2004/10/26/56804.html