cat /etc/issue

... to see what is your system version. Here is output from my PC:

Fedora release 14 (Laughlin)
Kernel \r on an \m (\l)

Anyway, repository installation with following command:

# add RPM Fusion repository with the rpm command
rpm -Uvh http://download1.rpmfusion.org/free/fedora/rpmfusion-free-release-stable.noarch.rpm
rpm -Uvh http://download1.rpmfusion.org/nonfree/fedora/rpmfusion-nonfree-release-stable.noarch.rpm

should resolve version issues and install without a problem. On the other hand, if you need to manually download/install rpmfusion-free-release package, make sure your system release and package release are matched.

what is that problem, help me.

su - root
yum install ...

# search for libvx library
yum search libvpx
# install libvx library
yum install libvpx

This will manually install VP8 Video Codec SDK. After installation of libvpx is finished try with media player installation.
Hope this tip will help.
Cheers!

[root@quadp5nd ~]# yum install vlc
Loaded plugins: fastestmirror, presto, refresh-packagekit
Loading mirror speeds from cached hostfile
* fedora: archive.fedoraproject.org
* rpmfusion-free: mirror.liberty.edu
* rpmfusion-free-updates: mirror.liberty.edu
* rpmfusion-nonfree: mirror.liberty.edu
* rpmfusion-nonfree-updates: mirror.liberty.edu
Setting up Install Process
Resolving Dependencies
--> Running transaction check
---> Package vlc.i686 0:1.0.6-1.fc12 set to be updated
--> Processing Dependency: vlc-core(x86-32) = 1.0.6-1.fc12 for package: vlc-1.0.6-1.fc12.i686
--> Processing Dependency: libmpeg2.so.0 for package: vlc-1.0.6-1.fc12.i686
...
...
...
---> Package vlc-core.i686 0:1.0.6-1.fc12 set to be updated
--> Processing Dependency: libtiger.so.5 for package: vlc-core-1.0.6-1.fc12.i686
---> Package xvidcore.i686 0:1.2.1-3.fc12 set to be updated
--> Finished Dependency Resolution
ffmpeg-libs-0.6-3.fc12.i686 from rpmfusion-free-updates has depsolving problems
--> Missing Dependency: libvpx.so.0 is needed by package ffmpeg-libs-0.6-3.fc12.i686 (rpmfusion-free-updates)
vlc-core-1.0.6-1.fc12.i686 from rpmfusion-free-updates has depsolving problems
--> Missing Dependency: libtiger.so.5 is needed by package vlc-core-1.0.6-1.fc12.i686 (rpmfusion-free-updates)
Error: Missing Dependency: libvpx.so.0 is needed by package ffmpeg-libs-0.6-3.fc12.i686 (rpmfusion-free-updates)
Error: Missing Dependency: libtiger.so.5 is needed by package vlc-core-1.0.6-1.fc12.i686 (rpmfusion-free-updates)
You could try using --skip-broken to work around the problem
You could try running: package-clean