A Facebook bug has been found recently that lets you create posts on your friends’ walls that can never be deleted.
Blocking means you no longer wish to be able to see or get in touch with a friend on Facebook, according to the warning that pops up when you click the button to block someone.
However, the agreement is only one-sided as the person you want to block will not be notified and all of the previously posted content will remain intact on that blocked friend’s wall but invisible to both of you.
All your posts to a friend’s wall will no longer be visible to you and your friend once you decide to block him or her. However, other unblocked friends will still be able to view your posts on that friend’s wall.
Facebook blocking does not include providing notifications to friends that you have blocked them, which means that the person you have blocked may not realize that you have posted something on his or her wall. Unless other Facebook friends notify a person about the wall post, the person will never even know about the invisible posts on their wall.
The fact that you can’t see something makes it impossible for you to remove it. Neither you nor the blocked friend can delete the post from his or her wall. The only way for both of you to view the post again is when you decide to unblock that friend on the site.