Password required restrictions on XP?

My mom has restrictions set on my brothers computer to where anything over a certain rating needs a password to access the site. Problem is it blocks one or two sites he is allowed on and she wants to set it up where the password is still there to keep all the other ones blocked but wants to put exceptions on for the one or two websites he is allowed on so she dont have to keep putting passwords in for him. He has a HP laptop and it runs Windows XP. How would she go about doing this?