This question already has an answer here:
I ran a terminal command and ever since I've been having problems.
The terminal command I entered was
echo off "deb http://archive.canonical.com/ubuntu/ $(lsb_release -cs)/partner Packages" | sudo tee -a /etc/apt/sources.list
I honestly can't even remember why I was doing this again but it was something I found off a forum. Ever since I entered the command,
sudo apt-get update doesn't work, and update manager has an error. Stating the following..
An unresolvable problem occurred while initializing the package information.
Please report this bug against the 'update-manager' package and include the following error message:
'E:Type 'off' is not known on line 57 in source list /etc/apt/sources.list, E:The list of sources could not be read., E:The package lists or status file could not be parsed or opened.'