error message when trying to go on icedove esr-channel

[Maja-O. Lenz]

Hi Mozilla team,

I am using icedove 3.1.16 and wanted to change to esr-channel following
the guide on http://mozilla.debian.net/ for testing (Wheezy).
But
deb http://mozilla.debian.net/ able icedove-esr
adding to my sources.list only resulted in the following error message:

W: Fehlschlag beim Holen von
http://mozilla.debian.net/dists/able/icedove-esr/binary-amd64/Packages
404  Not Found

E: Some index files failed to download. They have been ignored, or old
ones used instead.

What do I have to do?

Thanks,

Maja