1. Go to http://www.facebook.com and login
2. In the search box, search for the name of the person/page you want to unlike and click on them to go to their profile.
3. In the bottom left corner, you will see a link to UNLIKE (for pages) or UNFRIEND (for people).
4. Click on that link. To verifiy that it worked, you will see a new LIKE button (for pages) or ADD AS FRIEND button for people, showing that you are no longer linked to that page/person.