I think the header/metatag is designed poorly. The RTA proposal is that every operator of every site must verify the content and add the header to mark the site as "safe" or "unsafe". This is unnecessary burden that they have to bear if this proposal is given a green light and this is wrong.
Instead, the default should be, that if there is no header or it cannot be parsed, then the content is unsafe. And if there is a header, it describes the page rating, like what kind of dangerous content it may contain. The header may be added to any displayable content like HTML, text, images, audio or videos, but not to machine-readable content like JS files or AJAX responses.
So only those who wants their site to be accessible by minors, have to add headers. For social networks, the user might have an option to mark his content as "safe".
This means that with my proposal existing site operators need not to do anything to mark their sites as "unsafe" - all sites are "unsafe" by default. This means that millions of site operators need to spend 0 dollars to adapt their sites. How great is that?
The browser on a device with parent mode, should not allow displaying any content which doesn't have a header or that is marked as unsafe, or that contains header with invalid value. The parents may whitelist some sites.
There should be a reponsibility for intentionally marking unsafe content as "safe". We should also think what to do with foreign operators, intentionally putting invalid headers for unsafe content. Maybe they should be added to some kind of blacklist that the browsers would periodically update.
Search engines like Google could work by default in "safe" mode, but add "unsafe" header if the user wants to turn off restrictions.
> If a site is not adding the RTA header then progressively fine them into oblivion.
I think my proposal is better because it requires only fining those who intentionally misrepresent content safety.