There is a lot of porn online and most of it is not the the soft focused, girl next door type that I grew up with sneaking peeks at my dad’s Playboys. It’s definitely stuff you do not want your young children to see or come across accidentally (I’m not saying Playboy is okay – just that there is a big difference between that and online porn.) Here’s a recent piece from the Times on this issue
One place to start is this Google page, Safe Search Kids. Not only is it a safe search engine for kids which you can set as the default on your kid’s computer, it also has lots of information about general Internet usage and other alternatives.
One such alternative is Net Nanny. Net Nanny allows you, the parent, to set up criteria for what your child can view. It has built in levels based on age and maturity. It also gives you the ability to customize all the settings. For instance, you can set an option to warn about a site instead of explicitly blocking a site. Additionally, it can be set up to send you reports on all the sites that have been blocked or warned about.
Using these types of controls is a personal decision. There is no right or wrong. I do think it is important to discuss with your children why you are putting protection on their computers. This is not something that should create an adversarial relationship between you and your child.