I agree to Miss Mimi , on the fact that parents should moniter their kids internet activities.
Secondly i dont think any fliter can help to stop pronographic content, as its widely spread , even if I am on Facebook , i recieve an ad daily "try me free" with some really lucrative picture .... I know its spam , but for kids its not and they will definetly click, and same goes for many kids gaming sites , and then windows of infinite porn sites open ....
so their first impression of sexual activity , really can lead to frustration and then abuse... or may be victim
it surly is a parent job to moniter... for me no fliter nothing can work.