Error messages during updates

Are you getting error messages while trying to run:

apt-get update

?  Well here's a fix for ya.

This is the error I'm talking about specifically:

W:GPG error: http://ppa.launchpad.net hardy Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 7D2C7A23BF810CD5, W:GPG error: http://repository.cairo-dock.orgintrepid Release: The following signatures were invalid: NODATA 1 NODATA 2, W:Failed to fetchhttp://repository.cairo-dock.org/ubuntu/dists/intrepid/cairo-dock/binary-i386/Packages.bz2 Sub-process /bin/bzip2 returned an error code (2) , E:Some index files failed to download, they have been ignored, or old ones used instead.

There are two commands that need to be ran in succession to fix this:

 gpg --keyserver subkeys.pgp.net --recv 7D2C7A23BF810CD5
gpg --export --armor 7D2C7A23BF810CD5 | sudo apt-key add -

That's all there is to it!