The rule for firefox would appear to be limiting it to only one website. Not very useful for browsing…
With an AF of Low, all that is defined is the Application, Loopback (if used), and Direction of traffic. Assigning ports or IP addresses are good to “tighten” up the rules, but are really redundant at that point. The first time the application updates, you will get an alert that it has changed. When you click Allow w/Remember (which you’ll need to do, to stop the alerts for it changing), it will overwrite any and all details with only enough to match the AF Level. In this scenario, it will remove your IP address and Port restrictions, with Any and Any.
Same applies to GoogleDesktop (and it’s variants). My recommendation, at your current AF Level, is to select Allow & Remember for the FF and GD alerts. The necessary rules will be created. Then, when you get an alert based on ABA, you can either Allow w/Remember to not see that alert again, or simply Allow, realizing you will have to do so each time. Given that you use GD a lot, it seems (to me) pointless not to just “remember” the alert response, so as to minimize your regular popups.
In that case, if something “bad” happens, such as GD gets hijacked, or you get malware that tries to use either one to connect with, you’ll get a new alert. If you see that there is Library info that you’re not familiar with, or a new parent relationship of which you’re not aware, changed signature, etc, (always look at the details…), then it’s probably wise to Deny w/o Remember, and check out the situation to see if there’s a reason to be concerned. But for the day-to-day regular stuff, you’ll drive yourself crazy with popups if you don’t allow them more permanently.
The stuff you read about having AF Level on High is for those moderately-to-severely paranoid folks that want to know every detail all the time about how their system is connecting/communicating. They’re already crazy, so they can’t make themselves any worse by responding to popups. Their reflexes are lightning-fast, their eyes quick, and their fingers callused from super-clicking, so they are all set for that scenario… (:KWL)