how to install flash in Firefox for CentOS
* Go to youtube.com and try to play a video. You should not be able to play it
* Instead of the video, there should be a link like ‘Install Flash’
* You should be redirected to the Adobe website where you can download an RPM package
* After downloading it, install it with the rpm -i command (as root)
* Then, launch:
sudo yum install flash-plugin