How do you unblock someone from facebook?

First you scroll right down to the bottom of the page and click on 'Privacy'. Scroll down again and click on 'Privacy Settings' Then near the bottom of the page there should be three things that say 'Applications and Websites', 'Block Lists' and 'Controlling How You Share'. Click on 'Edit your lists' which is under 'Block Lists' and underneath the first two boxes there should be a list of people that you have blocked and you click unblock. This also works if u want to block someone (but the long way)

hope this helped!