Block: Go to the person's page that you want to block, and look on the left hand navigation links for BLOCK. Click on the BLOCK THIS USER link and approve the block.
UnBlock: Go to MY then to PROFILE , Change homestyle to POWER , Go back to your Homepage and on the right you will see "Who Viewed me " " who i viewed" And " Blocked" Click on the block tab, then " See all " and Unblock user