One of the nice things about MacOS X is the way it effortlessly adjusts to new network configurations and locations. Unfortunately, while the operating system does a good job with that, applications are a different story, especially when it comes to proxies.
Internet Explorer and NetNewsWire do a good job of using the system proxy information in the Network preferences panel, but only after stopping and restarting them. Mozilla ignores the system setting, having its own setting. The worst part of that is that it isn’t location-sensitive. I’m disappointed that Chimera hasn’t yet abandoned the Mozilla-style preference in favor of the system-wide setting, but hopefully that’ll come in a future release.