When comments or wall posts left on a friend's Facebook profile, posts, or pictures are later deleted, either 1) by the owner of the profile or 2) by the person who originated the post.
1) Occurs most frequently when comments are unflattering or incriminating. Also can be necessary to delete over posts left by the person you're casually banging, in attempt to lay claim on your or salt your game.
2) Often required after drunkbooking
1) "Dude-- don't write on my wall about getting wasted with me before work! Glad I post-censored you before my boss saw it!"
2) "I can't believe I wrote 'I love you' on my exes wall and commented on like 15 pictures.... I hope I post-censored before he woke up this morning!"