Preventing two browser tabs to share the same sessions values

Although I can't figure out what your purpose is, consider followings:
- cookies are linked to domains, thus if you use cookie based authentication and/or session, you can not separate the logins between tabs not even between browser instances (with one exception: due to it's purposes, "private" or "incognito" browser sessions are totally separated from the normal ones)
- thus if you want to be able to separate logins as you wrote, you have to disable cookies for session and authentication, see: http://msdn.microsoft.com/en-us/library/aa479314.aspx[^], http://msdn.microsoft.com/en-us/library/aa479315.aspx[^], http://www.asp.net/web-forms/videos/authentication/how-to-setup-and-use-cookie-less-authentication-in-an-aspnet-application[^]