Remove unofficial debian-multimedia.org repository from your sources

http://bits.debian.org/2013/06/remove-debian-multimedia.html

The unofficial third party repository Debian Multimedia stopped using the domain debian-multimedia.org some months ago. The domain expired and it is now registered again by someone unknown to Debian. (If we’re wrong on this point, please sent us an email so we can take over the domain! 😉 )

This means that the repository is no longer safe to use, and you should remove the related entries from your sources.list file.