Keep the computer in a central family location, not in the child's room. The computer shouldn't be an escape for the child, but a family activity. Get to know your children's online friends. You wouldn't let them spend lots of time with a new friend in the neighborhood until you've met them and know about them, online friends are no different. Screen e-mail with all younger children.
Many pedophiles attach child pornography to e-mails sent to children.
The child pornography is used to convince the child that other children are performing sexual acts. Make sure you screen all attachments or limit e-mail through parental control features or software. Help your children keep computing online in balance. Too many children get compulsive about computing and forget to play with real friends and never play outdoors in physical activity. Help them find a healthy balance.