Facebook allows you to connect with colleagues, friends and family all over the globe but also exposes you to the risk of cyber bullying and other forms of online harassment. A block prevents the offender from contacting you from within Facebook, however, it does not remove all traces of the person from your profile.
After blocking someone, he no longer can send you new messages within Facebook. Messages sent before the block, however, will remain. If you participate in a message conversation with a group of people that includes the blocked person, you can see his responses and he can see what you write. You can remove yourself from message conversions by opening the "Actions" menu from within the conversation and selecting "Leave Conversation." In addition, you can manually delete existing messages at any time.
Once you block someone, he cannot view or post to your profile wall and vice versa. Posts made before the block continue to appear. You can remove any post you find offensive or problematic from your wall by clicking the blue "X" that appears when you place the mouse cursor over the post. In addition, the blocked individual cannot see new posts or comments you make on the wall of mutual friends. Comments or post you made on a mutual friend's wall before the block, however, remain visible.
Blocking someone does not prevent you from viewing the photos he tagged you in before the block. If the person removes the tag, however, you no longer can see the photo. The blocked person cannot view any tagged photos of you, even if the photo belongs to a mutual friend.
Blocking a person within Facebook does not prevent contact from within third-party Facebook applications or other communication forums. Take the necessary precautions to protect yourself if the person you blocked continues to exhibit threatening behaviour.