Want to keep your kid from looking at porn on the Internet (when they actually want porn I mean)? Here are two sure-fire tools to make this happen... Ready?
1. Do not allow your kid unsuperised access to the Net. Ever. If your kid can masturbate to porn with you watching him then your childs issues would be better dealt with by institutionalization.
OR
2. Do not allow them acces to the Net at all. Ever.
There ya go folks.
It is just that easy. If this is too hard for you then just own up to the fact that your time is more important to you than your children's porn habit. That's easy too.