W: A error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://extras.ubuntu.com natty Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 16126D3A3E5C1192

W: A error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://dl.google.com stable Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY A040830F7FAC5991

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 048A1684108A879C
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 0ED8DB2BB4CFE229
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 F2A97597D5056DDE
W: Failed to fetch http://extras.ubuntu.com/ubuntu/dists/natty/Release

W: Failed to fetch http://dl.google.com/linux/chrome/deb/dists/stable/Release

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