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?