Question : Proper Token Usage...

I need to create a website that provides me with the ability to identify the user and his/her progress through the site using some sort of token.  Once this token is generated, would it be better to persist the token in a cookie or to pass it from page to page using a session variable?  This token will be passed into various web services as well.  Any thoughts or assistance would be appreciated.  Thanks.

Answer : Proper Token Usage...

I solved this problem:

In fact it was because I was having circular references:

user have a group, and groups have users, etc.

I solve this by using the [DataContract(IsReference = true)] tag on my POCO objects, like mentionned here:
http://www.mostlydevelopers.com/mostlydevelopers/blog/post/2009/02/03/Fixing-WCF-Circular-Reference-Serialization.aspx