Intego ContentBarrier filter software for Mac $27.35
If you need to filter this is how it should be done.
Not sure if this is any better than Macs built in filtering Parental Controls, but Intego software has a good reputation.
'ContentBarrier sets up a protective wall around your computer. Its predefined categories let you choose what you dont want your children to see, and you can also create your own custom categories.
ContentBarrier blocks adult web sites, sites with subjects not fit for children, and even blocks chats when predatory language is used. It blocks offensive content coming from the Internet. ContentBarrier works with multiple users; if you have several children, you can set different criteria, corresponding to their age or maturity
You can choose whether they have access to newsgroups or whether they can download files. You can set the program to let them only use the Internet at certain times, and on specific days.The program can even send you e-mail, automatically, when certain events occur. ContentBarrier keeps a complete log of all web sites visited, whether blocked or not.'