W: GPG error: http://ppa.launchpad.net natty Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 7BB206E130C58366
W: Failed to fetch http://ppa.launchpad.net/openjdk/openjdk/ubuntu/dists/natty/main/source/Sources  404  Not Found

W: Failed to fetch http://ppa.launchpad.net/openjdk/openjdk/ubuntu/dists/natty/main/binary-amd64/Packages  404  Not Found

E: Some index files failed to download. They have been ignored, or old ones used instead.