bad sign

shanazsoft:/home/ibrahim# apt-get update Get:1 http://www.debian-multimedia.org sid Release.gpg [189B]
Get:2 http://ftp.no.debian.org sid Release.gpg [189B]
Hit http://ftp.no.debian.org sid Release
Err http://ftp.no.debian.org sid Release

Get:3 http://ftp.no.debian.org sid Release [79.6kB]
Get:4 http://www.debian-multimedia.org sid Release [5560B]
Ign http://www.debian-multimedia.org sid/main Packages/DiffIndex
Get:5 http://www.debian-multimedia.org sid/main Packages [45.4kB]
Ign http://ftp.no.debian.org sid Release
Hit http://ftp.no.debian.org sid/main Packages/DiffIndex
Hit http://ftp.no.debian.org sid/contrib Packages/DiffIndex
Fetched 131kB in 7s (16.5kB/s)
Reading package lists... Done
W: GPG error: http://ftp.no.debian.org sid Release: The following signatures were invalid: BADSIG A70DAF536070D3A1 Debian Archive Automatic Signing Key (4.0/etch) <ftpmaster@debian.org>
W: You may want to run apt-get update to correct these problems
shanazsoft:/home/ibrahim#