Facebook wall posts allow you to keep in touch with your friends, share links and comment on each other's photos. Depending on how you've set up your Facebook account's privacy settings, your friends may be able to post on your wall in addition to you posting on your own.
A post left on a Facebook Wall remains there indefinitely, as long as the owner of the account keeps his account active. Over time, depending on how often people post on the wall, posts are pushed down toward the bottom of the page. As newer posts appear on the wall, older posts disappear, but you and other users can still access them.
To view older posts, scroll down to the bottom of the wall and click "Older Posts." You can continue scrolling down and pressing "Older Posts" to date back to the point at which you created the Facebook account.
Though Facebook wall posts remain up indefinitely, they can be deleted for a couple of different reasons. If you no longer want the message to appear, whether you wrote it or someone else wrote it, you can click the "X" button to the right of the post. If a friend decides he doesn't want his message to appear on your wall any longer, he can delete it, too.
Your Facebook account's privacy settings dictate who can post on your wall and who can read posts on your wall. Under your account's privacy settings tab, you can choose, for example, whether friends, friends of friends or everyone can see your wall posts.