[SOLVED] Ubuntu isn't updating for last 20 days

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http://ubuntuforums.org – Hi, I'm facing a very annoying problem while trying to update my Ubuntu 12.04 for last 20 days. When I'm clicking the Check button in the Update Manager window, it starts to fetch the new update information but after almost 1 minute a new dialogue box is opens and says that Code: Failed to download repository information Check your Internet connection. W:Failed to fetch http://ppa.launchpad.net/https/ppa/ubuntu/dists/precise/main/source/Sour... 404  Not Found , W:Failed to fetch http://ppa.launchpad.net/https/ppa/ubuntu/dists/precise/main/binary-i386... 404&nbsp (Hardware)