Private String is a private wall that works as a Facebook application or a standalone website. You can invite friends to private groups where only they can see your status updates, pictures, comments, likes/dislikes and groups wall.

You can set messages to self-destruct either by time or can manually destruct them at anytime by clicking the X in the upper right corner.

When you delete a comment or a post, you will see an undo button. This gives you about 20 seconds to change your mind. If you do not undo it, the post self-destructs automatically.

You can create as many groups as you want. To add and delete friends, go to the manage group settings. Only the members of the group will be able to see each others comments and wall.

You can post the same message to multiple groups so that each group can your message. However, the groups will not be able to view each other's wall, keeping the comments, likes and dislikes, private within groups.

You can invite friends from facebook using the Facebook Invite Button in the top left of the screen, or you can search for your friends, using the "search" bar above your friends list.

When a message self destructs, it is removed from your groups wall, and by default instantly deleted from your wall. You can adjust the time before deletion in Setting > Profile Setting > "Permanent Deletion Time after Self Destruct".

By default your string is set to private. If you want to change this to public, you can do so in the profile setting. If your string is set to Public, then any public posts will be viewable, even to people not in your string or friends list.

Yes.

To delete a friend, go to their profile and click remove friend.