[CentOS] yum updates not working

Fri Sep 19 18:06:20 UTC 2014
Joseph Godino <jgodino5 at gmail.com>

I think my software updates are not working. I know a Firefox update was
announced yesterday but when I try sudo yum update I get a message
saying that no packages are marked for update. I tried sudo yum clean
all but I still get the same response.
Any suggestions?