How do i simulate two users in a two browser in a single machine?

Question

hi,
In Win forms this is a piece of cake, but how do i similate two user in a machine using a web brower. I have tried this using the session object that stores the user name and password of a user if the login is valid then user is directed to his home page. I can opne anohter brower and do the same with a user therefore two users have logged on the server. But if i logout a user (any) and i refresh the second users home page it directs me to the login page. But this should not happen. this happense because i have cleared off the "UserName" session variable in the session object. How do i store two or more user names in a session object and if a user logs out only that user's "UserName" should be deleted and other should remain...thus i expect if others refesh their home page they remain in their home pages and should not be directed to the login page....
TY