GPG error while "apt-get update"

Error example:
GPG error: http://ppa.launchpad.net intrepid Release: The following signatures couldn't
be verified because the public key is not available: NO_PUBKEY CB2F6C86F77B1CA9

Solution:

Type: gpg --keyserver subkeys.pgp.net --recv CB2F6C86F77B1CA9
Responses:
gpg: requesting key F77B1CA9 from hkp server subkeys.pgp.net
gpg: /root/.gnupg/trustdb.gpg: trustdb created
gpg: key F77B1CA9: public key "Launchpad PPA for Timothy Pearson" imported
gpg: Total number processed: 1
gpg: imported: 1 (RSA: 1)

Type: gpg --export --armor F77B1CA9 | sudo apt-key add - F77B1CA9
Response: OK

Type: apt-key list
Responses:
...
pub 1024R/F77B1CA9 2009-01-22
uid Launchpad PPA for Timothy Pearson

Repeat steps above for every key mentioned on the error msg

Done! Now try again: sudo apt-get update