In the Facebook javascript api there is a login function in which you specify extended permissions: http://developers.facebook.com/docs/reference/javascript/FB.login

One of these permissions is offline access. So I can save the facebook user's session key and assume it will not expire for a long time. The question I have is simple - how do I use the session key? I understand that the session key will last longer, but I don't understand how to use it in the Facebook API. For one of my products, a user must restart his/her browser and I would like to recognize them when they restart. The problem is that they are logged out of facebook, so they must login on my site again where I would rather just use offline access. Sample code would be great!

Thanks