I found a script that will do this but I'm wondering if there is a way to modify it so that it makes the user confirm once more that they accept. Maybe have another alert that asks them:
Please choose OK to accept the terms or Cancel to exit.
Can this be added?
//Accept terms & conditions script (by InsightEye www.insighteye.com)
if (f.agree.checked == false )
alert('Please check the box to continue.');
<form action="/yourscript.cgi-or-your-page.html" method="GET" onsubmit="return checkCheckBox(this)">
<!--Enter your form contents here-->
<b>By submitting, I agree that all info entered was done accurately & truthfully.</b><br>
I accept: <input type="checkbox" value="0" name="agree">
<input type="submit" value="Submit form">
<input type="button" value="Exit" onclick="document.location.href='/index.html';">