The leading online services offer relatively straightforward controls. AOL and MSN have suggested settings for different ages that can completely block kids' access to, say, instant messaging or chat rooms. If kids want access to a blocked website, they can e-mail a request to their parents, who can in turn view a complete list of sites their kids have visited and set limits on how long they can stay online.
If your kids access the Web from a regular Web browser, however, you have to do a little more work. While there is a built-in Content Advisor in Internet Explorer and a SafeSearch feature in Google, I found both ineffective: they either fail to block pornographic websites altogether or block so many sites that your browser becomes unusable. (For example, I was unable to log on to the Nickelodeon kids' site nick.com using Internet Explorer's Content Advisor.)
A pricier but more effective option is a filter that you download from the Internet. Of the three programs I tested, Cyber Patrol, Cybersitter and Net Nanny, only one seemed impervious to smut: Cybersitter. This $40 program (available at cybersitter.com) can run in a stealth mode so your kids don't notice it's there. When they try to log on to a blocked site, they are presented with either a blank page or a standard error message that reads, "This page cannot be displayed." Cybersitter works on e-mail, instant messaging, newsgroups and file-sharing sites. A System Snooper feature enables you to scan your hard drive for evidence of "recent internet activity where potentially objectionable material has been accessed." One downside to Cybersitter: it doesn't work on Macs.