I also want to climb up on my soapbox for a minute:
Your best defense is to put the computer in a public place with the screen facing out, and walk by from time to time. When issues come up, deal with them. Make it clear what the ground rules are, e.g., "We do not tell anybody our name, address, phone or any other personal information, not even to win a free iPod."
The enemy on the Internet is not pórn. The enemy is unregulated CHAT.
Many people find Pórn repugnant, but Pórn will not arrange to meet your youngster after school.
Thanks for the replies. I did manage to get Safari working now without crashing--not sure what was going on before, but once I set up a new account it worked. I'm setting up all the parental controls available via the OS and Safari. And yes, he sits right in full view of us at the kitchen counter when he's on this machine!:)
You can change your routers DNS to OpenDNS servers.
DNS - Domain Name Server resolves the name of the web site into a IP Address like 67.342.565.343 which the computer uses to connect to another computer.
This is used in case a web site changes servers, they keep the name, just change the location. DNS automatically solves the location issue for people.
But it also can be used as a content filter, which OpenDNS does with a free service.
What you have to do is acces your router and change the two DNS IP addresses to OpenDNS servers.
Then sign up for the "home free" account at OpenDNS and set the controls, Pr0n, web proxies, hostile sites and so forth. Then OpenDNS will filter out about 90% of the hostile stuff out there, which is enough for the occasional stray/non tech user.
Hard core types who know the name of the site they want to visit (say yourself for example like a particular adult site) can use netcraft or whois to find the current IP address of the site, then punch in the IP number manually into their browser URL address field and go to the site directly, without needing a DNS lookup.