Ok, it's because of the Debian deb-src in /etc/apt/sources.list.
$ apt-cache madison filezilla filezilla | 3.0.7.1-0ubuntu1 | http://archive.ubuntu.com hardy/universe Packages filezilla | 3.0.7.1-0ubuntu1 | http://archive.ubuntu.com hardy/universe Sources filezilla | 3.0.0~beta2-4 | http://ftp.fr.debian.org unstable/main Sources filezilla | 3.0.7.1-1 | http://ftp.fr.debian.org experimental/main Sources
contains "main".
Ok, it's because of the Debian deb-src in /etc/apt/ sources. list.
$ apt-cache madison filezilla archive. ubuntu. com hardy/universe Packages archive. ubuntu. com hardy/universe Sources ftp.fr. debian. org unstable/main Sources ftp.fr. debian. org experimental/main Sources
filezilla | 3.0.7.1-0ubuntu1 | http://
filezilla | 3.0.7.1-0ubuntu1 | http://
filezilla | 3.0.0~beta2-4 | http://
filezilla | 3.0.7.1-1 | http://
contains "main".