是否可以在Web Session中进行会话

I am developing an application where I need to support multiple instances of browser on same machine but with different user logins ! As far as if we open two different IE process instances, there will be different sessions on server side but same is not the case for Firefox (correct me if I am wrong). So is there any way I can somehow link the login specific information with every HTTP requests (GET / POST) going to web server. I am exploring URL rewriting / cookie but not getting proper idea. I am developing an application where I need to