Mine look like this:
#
# deb cdrom:[Debian GNU/Linux 7 _Wheezy_ - Official Snapshot i386
LIVE/INSTALL Binary 20140209-19:55]/ wheezy main
deb http://ftp.us.debian.org/debian/ wheezy main
deb-src http://ftp.us.debian.org/debian/ wheezy main
deb http://security.debian.org/ wheezy/updates main
deb-src http://security.debian.org/ wheezy/updates main
# wheezy-updates, previously known as 'volatile'
deb http://ftp.us.debian.org/debian/ wheezy-updates main
deb http://linux.dropbox.com/debian wheezy main
deb-src http://linux.dropbox.com/debian wheezy main
deb-src http://ftp.us.debian.org/debian/ wheezy-updates main