Due to the way cookies (and hence sessions) work, the behavior of anybackends that make use of cookies or sessions is undefined when the sameclient makes multiple requests that set or get messages in parallel. Forexample, if a client initiates a request that creates a message in one window(or tab) and then another that fetches any uniterated messages in anotherwindow, before the first window redirects, the message may appear in thesecond window instead of the first window where it may be expected.