When I want to install the SMPlayer from http://smplayer.berlios.de/downloads.php?tr_lang=en,

I have a problem which is
W: GPG error: http://ppa.launchpad.net hardy Release: Release: The following signatures couldn’t be verified because the public key is not available:  NO_PUBKEY @@@@@@@@@@@@

The solution is
gpg --keyserver subkeys.pgp.net --recv @@@@@@@@@@@@
gpg --export --armor  @@@@@@@@@@@@  | apt-key add -

by using the following references 
posted by citadel