Unfortunately, there’s a limit to how much protection can be offered to children who use the internet. But in my opinion that protection needs to start in the home with the parents. Parents need to educate their children on the dangers of the Internet and how predators operate online (grooming etc). They also need to limit their children’s access to certain websites that can be potentially dangerous. Finally, they should be monitoring their children’s use of the Internet on a regular basis.
As for websites, there are certain measures they can take to make children safer when they use their site. One is having age restricted rooms. Another is posting warnings and guidance on how to use their site safely. They can also have staff who monitor the rooms to reduce the amount of predators, and to act as a resource the child can talk to if they have a problem or a question. The site can also work with LE so that when a predator is identified, they can be criminally prosecuted.
None of the things mentioned above are fool-proof, and we don’t live in an ideal world. Those are just some things, in general, that can hopefully help.