Session management for security
http://en.wikipedia.org/wiki/Session_%28computer_science%29
http://security.stackexchange.com/
http://www.codinghorror.com/blog/2010/11/breaking-the-webs-cookie-jar.html
http://news.netcraft.com/archives/2003/01/01/security_advisory_2001011_predictable_session_ids.html
http://randomcoder.org/articles/jsessionid-considered-harmful