If you have kids and want to protect them from visiting the wrong sites on the internet, you should know about K9 Web Protection. It comes pre-configured with a list of sites that are blocked. You can add to the blacklist, and you can whitelist certain sites as well.
K9 also allows you (as the administrator, via a password-protected interface) to schedule web availability for only certain times of day.
K9 is free. The only disadvantage of K9 is that you need to install it on each machine that your child might potentially use. If this is not feasible, there are other options.
Many routers allow you to set up content filtering and availabilty scheduling.
OpenDNS is another, more technical, option. It replaces your isp’s DNS server (the thing that translates domain names into ip addresses) with that of OpenDNS. For more info visit www.opendns.com.
Be aware that filtering using your router settings or OpenDNS will effect every computer on your network, including the one you use.
Wishing you and your family a safe and happy holiday!