Here is how it works: when a visitor enters the site the page is blocked with a transparent cover and there is a popup to confirm you are of the right age (or other purposes).
Here is an example, click on the "Member Login" to see how it works:
[url removed, login to view]
I would need such thing and willing to pay. The code needs to work flawlessly with any php scripts and ideally with .html files too.
A plus would be if it could work based on IP so it does not show again on the same IP.