FoxyProxy is a firefox extension which allows advanced proxy configurations.
FoxyProxy | Firefox Add-ons | Mozilla Corporation
FoxyProxy is an advanced proxy management tool that completely replaces Firefox’s proxy configuration. It offers more features than SwitchProxy, ProxyButton, QuickProxy, xyzproxy, ProxyTex, TorButton, etc
FoxyProxy will let you define profiles for your proxy configuration. For example if you have a laptop, you might need a profile with the corporate proxy, while you’ll prefer direct internet connection when you’re home.
Or you might prefer to use one proxy to reach a website, while using another for another one.
FoxyProxy will be able to switch profile automatically (based on wildcards / regexps) or let you choose manually the profile.