I've been using this for a while now and have experienced no problems with crashes or odd behaviour. The features of this software far surpass many competitors.

This free software enables the administrator on the machine to select which categories should be blocked and also allows time limits for Internet usage to be enforced.

While the software does refer to an extensive blocklist, the software makes an intelligent guess as to the nature of those sites not already categorised. The software offers the ability to submit sites for review that you consider are incorrectly labelled or not labelled at all. I have submitted quite a few sites and the turnaround from submission to judgement and re-categorisation has only been a few hours. You can also add sites to your own personal blocklist if desired.

I've tried several content filters in the past and have also used OpenDNS to enhance my content filtering. This is by far the best one I have used, and given that it is FREE makes this one head and shoulders above the rest.