How would you add a warning page but...

I cant change the page on the root directory... I think I have seen a couple sites be able to do this:

have the main page of the adult site index page in the root directory, but for 1st time visitors to the site maybe using a htaccess redirect the surfer to agree to the terms including "must be 18 or older to view".


Maybe using cookies that expire every 30 days or something... is this possible programmers?

I want my main page to be the index file of the root directory, but you are a 1st time surfer going to www.domain.com and you get redirected to a warning page before entering the index page in the root directory. Also, all my traffic trades not to get redirected for those auto crawler programs.


I hope this is clear, I am asking if this is possible?


Thanks,
Chuck