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Please let me know how to remove certain repositories in Ubuntu 11.04. I am getting the following errors while updating.
sudo apt-get update
Err http://ppa.launchpad.net natty/main Sources 404 Not Found Err http://ppa.launchpad.net natty/main i386 Packages 404 Not Found ...... E: Some index files failed to download. They have been ignored, or old ones used instead.