Hi!
I would like to be shown a "yes/no" modal dialog in my forum when user enters in a certain board, and only can enter when the "yes" button is clicked. For example: Are you 18+ years old? yes/no. I have seen such a thing on some phpBB forums.
There's no option for it and to be honest I'm not sure what benefit it would actually be... users have a curious habit of lying about such things.
Oh, yes, but it could stop autoposters...
Maybe. Maybe not. It would stop search engines coming to your site.
There are better ways to stop spam bots.