The simple way which you can copy and paste into the body of your page is as follows:
if (!confirm("Type your message here to warn people that by proceeding they are agreeing to your terms and conditions........... Press <OK> to enter. Press <Cancel> if you want to change your mind.......... "))
history.go(-1);return " "
Note that all you get from this is a pop up message with your typed warning that proceeding beyond that point assumes that your visitor is agreeing to your terms and conditions. If you want full on page redirecting and protected areas, you need to start thinking about ASP pages or similar. If someone knows or guesses that say, a page called URL/page2 . htm is where they want to go and your warning/terms and conditions/page redirect is on URL/page1 . htm, all they need to do is type in the relevant address.
About the quickest way to control access to pages that I know of for anyone, whether you are technically minded or not, is the excellent CoffeeCup Password Wizard from click here
If you need something more sophisticated than the above, post again.