What about dog tails?

I believe this was brought up before but......What do the signs of dog tails mean (fear,friendly,want to play) ? When a dogs tail is straight down, curve upward Ect.?

I know that a wag is rather happy or confused. Tail down usually means sadness or guilt. Tail curled up is in some cases a natural way to hold the tail (Tango does this). I am not sure about the rest.

Here's a site with some pictures of dog postures:

http://dukkie_cave_canem.tripod.com/dogslife.html

Great Aly, just what I was looking for!