It's worth remembering that although you can probably control a 9-year old child's use of the internet to a large extent you will not be able to do so for very long. Children very rapidly learn how to circumvent parental controls - usually by picking things up from other children at school.
An average child of 10 or eleven years of age will learn very rapidly, and will quickly be able to run rings around the average parent when it comes to computer literacy. Children are intensely curious, and telling them that certain things are forbidden is likely to stimulate that curiosity even further. It's a bit of a losing battle as far as all but the very strictest parents are concerned.
Sometimes I'm asked to sort out sluggish computers in the homes of clients and colleagues, and if children are using the machines I can almost guarantee that I'll find evidence of surfing activities which wouldn't entirely please the parents.