If you unsubscribe from a friend on facebook then resubscribe, will they know?

[jny]

I think if you unsubscribe a friend, they do not get a notification so they won't know. But if you subscribe to their updates again later on, will they get some sort of notification telling them that?

Also, if you delete a friend from facebook, will all the previous wall posts you put on their wall disappear too?

[balloon]

I don't know about the second one but for the first one:
Nope.

[Smokies Hiker]

No, they won't know about your departure and return. All postings on a persons facebook page are their property, and remain until the owner removes them. You can delete the friend, but your posts will remain.