>I've made a change to my web.config on our live server. When does this change become active? IISResart, server reboot? In particular I've changed the sessionstate value, and despite closing my browser and authenicating again, the sessionsate is still at the old value.

Changes are immediately upadated. THe way this works is that ASP.Net senses the change and releases the AppDomain that hosts the ASP.Net runtime and starts a new one. Actually it starts the new one first and leaves the other running until all pending requests have released.

This is pretty cool actually. I use a COnfigurtation class that has hard properties for config value in an all Static class. This class' static constructor reads the settings from the Web Config file (and does some post processing on most of that) - and this class also fires as soon as Web.config is changed.