>There are probably reasonable ways for the government to do this. Some kind of government run validation website where a user can generate a code to validate their age to each individual website is probably ok (in the UK we have a similar system for providing driving licence information to rental companies for example).

Why not just the parent sets the child device to "kid mode" and that is it. otherwise how do you make different national systems work World wide ?

Your idea is valid but seems much more harder to implement. With my proposal where the parent and the OS vendor collaborate on this seems much more flexible and would work even better, like religious extremists could configure their child and their own devices to block much more then porn.

I'm mostly with you. In fact I've often wished that browsers did more things like that, for example cookie warnings. The cookie warning thing is a ridiculous misunderstanding of how things should work. The server doesn't store things on your PC, it just offers them to your browser, it's up to the browser to return them or not, it doesn't even require new protocols.

But of course kids are resourceful and will find a way of accessing content they want to access, for example maybe using a games console or something a parent might not immediately think of as having a browser.

Whether it actually makes sense to protect kids from themselves to that extent I think is a valid question which I'm not sure I have the answer. I know passing around CDs full of such content was common when I was young (in the early days of the internet).