Opening multiple tabs or windows into your Arts People system is not recommended. Since the system uses a "session" identifier within your browser, you could end up having odd behavior or errors or get kicked out and have to relog in. There are some cases where this can be used, such as working on a venue design, saving, and looking at the venue on the public pages screens in another tab by refreshing the screen, but in general we cannot recommend this practice due to possible errors.
You can have multiple browsers logged into the system, since the session key is linked to the browser. So you could have Google Chrome and Firefox browsers both logged into your system at once on your computer, and this should cause no complications. Be cautious of attempting to work on the same data in two browsers at the same time however.