Thanks for your information.
It seems Skype doesn't provide the amd64 version of Skype for Linux, there's http://download.skype.com/linux/repos/debian/dists/stable/non-free/binary-i386/skype-2.1.0.81-1_i386.deb
But no amd64, so I will try to disable the source display in Ubuntu Tweak.
Thanks for your information.
It seems Skype doesn't provide the amd64 version of Skype for Linux, there's http:// download. skype.com/ linux/repos/ debian/ dists/stable/ non-free/ binary- i386/skype- 2.1.0.81- 1_i386. deb
But no amd64, so I will try to disable the source display in Ubuntu Tweak.