I got this warning when I installed my first package in freshly installed fedora 14. Thought it would help those few ppl who might get the same error as mine.
The first package I installed is VLC. After downloading the required packages and dependencies, I got a warning.

warning: rpmts_HdrFromFdno: Header V3 RSA/SHA256 Signature, key ID 865cc9ea: NOKEY

and the installation stopped :(

This is because, I had installed an older version of rpm repositories.

To recover from this error,type

su -c
yum localinstall --nogpgcheck http://download1.rpmfusion.org/free/fedora/rpmfusion-free-release-stable.noarch.rpm http://download1.rpmfusion.org/nonfree/fedora/rpmfusion-nonfree-release-stable.noarch.rpm

Of course, this is not the only way to do this.. The other easy way is to download the repositories manually by clicking the rpm file.. (as mentioned in my old post )

The target is to update your repositories. No matter how you do it. Now yum works perfectly fine. :)