Warning Page requirements?

[Alphawolf]

Did a search and didn't find exactly what I was looking for here.

I'm designing my entrace page and wondering what is required or what should be on the warning page?

First off, I'd put a warning anyway, but is it required? Seems like some sites put a very mild warning:

http://www.mystique-magazine.com/

Is the warning page for legal reasons or just good practice among webmasters and a requirement for some links lists?

I like http://www.hustler.com 's approach. But I've also seen sites with giant forms and terms of agreements.

So, what is considered a 'best practice' for one's warning page as far as what specifics to put on it?

Is something like:

"You have reached an Adult Website intended for people 18 and over ONLY. If you are under 18 or an adult that finds photos of nude sexual erotica offensive, you don’t belong here and must leave immediately."

...kosher?

TIA