apt-get update returns error 404 because of iceweasel

Since Debian uses firefox instead of iceweasel, apt-get update returns 404 errors with this URL: http://mozilla.debian.net/dists/wheezy-backports/iceweasel-release/binary-amd64/Packages I had installed firefox-esr in order to migrate to firefox and I have no problem, I can use Firefox. I use rvm and when I try to install ruby with it, it stop the installation because apt-get update returns a error 404. Read this. I use Kali Linux and my sources.list is clean: #kali 2.0 deb http://http.kali.org/kali sana main non-free contrib deb http://security.kali.org/kali-security/ sana/updates main contrib non-free How to delete these 404 errors?