If you are logged off in a Member area, and your Membership expires, you will be returned to Ravenwood Commons and you can continue to play in the Free to Play areas of Wizard101.
You will not be able to access Premium zones unless you purchase another Membership or buy the individual areas with Crowns.
I was wondering what happened if you logged off in a membership place and then is it expired when you were offline, when you logged back on. thanks for telling me what would happen lol