DansGuardian is an award winning Open Source web content filter whichcurrently runs on Linux, FreeBSD, OpenBSD, NetBSD, Mac OS X, HP-UX, andSolaris. It filters the actual content of pages based on many methodsincluding phrase matching, PICS filtering and URL filtering. It does notpurely filter based on a banned list of sites like lesser totallycommercial filters. DansGuardian is designed to be completely flexibleand allows you to tailor the filtering to your exact needs. It can be asdraconian or as unobstructive as you want. The default settings aregeared towards what a primary school might want but DansGuardian puts youin control of what you want to block.