Problem with the "sudo apt-get update" command

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http://askubuntu.com – I'm a beginner when it comes to the Linux environment. I recently tried to install some extensions in Linux. I've entered some commands like: sudo apt-get install gnome-tweak-tool and then when I tried to update with: sudo apt-get update I received this message: E: Type 'ME' is not known on line 2 in source list /etc/apt/sources.list.d/gnome3-team-gnome3-precise.list Each time when I want to update I receive this error. Does anyone have any ideas as to how I may correct this problem? (HowTos)