Mac OS X: Bypassing proxy settings for specific IP addresses

If your computer is connected to a local network that’s protected from the Internet by a firewall, you may need to specify proxy servers to access some Internet sites. A proxy server is a computer on a local network that acts as an intermediary between a single computer user and the Internet so that the network can ensure security, administrative control, and caching service. You can also choose to bypass proxy settings for specific computers on the Internet (hosts) and segments of the Internet (domains) by adding the address of the host or domain in the “Bypass proxy settings for these Hosts and Domains” field.