REfer
http://code.msdn.microsoft.com/CSASPNETCurrentOnlineUserLi-95eb624f
http://www.c-sharpcorner.com/Blogs/9541/find-online-number-of-users-on-a-website.aspx
http://forums.asp.net/t/1216009.aspx
http://ruchitech.blogspot.in/2012/06/show-online-usersvisitors-in-aspnet.html