How Can Internet Access by Children be Controlled?

How Can Internet Access by Children be Controlled?: "Nowadays, everyone can access internet easily, including children. Unfortunately, for children, internet not only provides positive things, such as knowledge, information, education materials, and others; but also brings negative effects. For instance, it allows them to open adult websites, gamble or buy goods on credit. Therefore, parents and society have to pay more attention to control internet use by children."