I have a website where you're supposed to be 21 or older to buy the wine from this site. How do I put an "alert" up stating that by clicking through to the buy pages you certify that you are 21 years or older?
Page 1:
You must be 21 or older to buy wine from this site. By clicking, blah blah blah, legal disclaimer, etc. Contains a link to Page 2.
Page 2:
The main website.
I think Randolpho's suggestion is a little too annoying. I think you should just put text next to the 'Buy' button that says 'By Purchasing, you are acknowledging you are 21 or older.'
I also like the way Google has done some of their buttons. They make the button say 'You Agree to Terms and Conditions'. It is much easier than a checkbox.
Note: Just realized forums have been doing it this way for years. lol.
But in all honesty, the least intrusive way to do it without hiding it at the footer, is to either make it the button, or put a note next to the button. That way there are absolutely no extra steps.
BTW, Like Andrew IANAL.
In addition to being a software developer, I am also a lawyer. IMO, from a legal perspective, you are in much better position to require everyone to register and that the act of registering - requires acknowledging a specific assertion that the user is indeed over 21. In the event the crap hits the fan, you have something affirmative in the system that can be referenced. I would also put a disclaimer at the foot of every page.
Probably not the tech answer you were looking for...but legally, I think it will help you.
To answer your specific question, something like this in your main page could help...
<script language="javascript" type="text/javascript">
alert('By entering this site, you certify that you are at least 21 years of age.');
</script>
Hope that helps...
The way that http://www.wine.com does it, is by requiring you to create an account to buy something, which requires a first name, last name, e-mail, password, zip code and date of birth. Next to the DOB field it says "(Must be 21 yrs old)."
Simple to do and not annoying for users.
In this case, I think it is best to check out how the competion handles themselves and mimic the functionality. As previously mentioned, wine.com requires an account and age validation/acknowledgement. I suggest you do the same -- EXACTLY the same -- thing.