Install Adobe Flash for your Firefox on Cent OS...

This is guide, howto install Adobe Flash Player Plugin version 11.2 (32-bit and 64-bit) with YUM on Fedora 17/16/15/14/13/12, CentOS 6.2/6.1/6/5.8 and Red Hat (RHEL) 6.2/6.1/6/5.8. Using Adobe’s own YUM repository it is very easy also keep up-to-date with Flash Player Plugin. Finally also native 64-bit (x86_64) version of Adobe Flash Player is available for Linux users.
1. Change Root User

sudo -i
## OR ##
su -

2. Install Adobe YUM Repository RPM package

## Adobe Repository 32-bit x86 ##
rpm -ivh http://linuxdownload.adobe.com/adobe-release/adobe-release-i386-1.0-1.noarch.rpm
rpm --import /etc/pki/rpm-gpg/RPM-GPG-KEY-adobe-linux

## Adobe Repository 64-bit x86_64 ##
rpm -ivh http://linuxdownload.adobe.com/adobe-release/adobe-release-x86_64-1.0-1.noarch.rpm
rpm --import /etc/pki/rpm-gpg/RPM-GPG-KEY-adobe-linux

3. Update Repositories

yum check-update

4a. Install Adobe Flash Player 11.2 on Fedora 17/16/15/14/13/12, CentOS 6.2/6.1/6 and Red Hat (RHEL) 6.2/6.1/6
Fedora 17/16/15/14/13/12, CentOS 6 and Red Hat (RHEL) 6 32-bit and 64-bit version

yum install flash-plugin nspluginwrapper alsa-plugins-pulseaudio libcurl

4b. Install Adobe Flash Player 11.2 on CentOS 5.8 and Red Hat (RHEL) 5.8
CentOS and Red Hat 32-bit and 64-bit version

yum groupinstall "Sound and Video"

yum install flash-plugin nspluginwrapper curl

5. Verify that the Flash Player Plugin is working

Open Mozilla Firefox and write about:plugins on address bar. Results should look like following:
Adobe Flash Player 64-bit installed on Fedora 16 64-bit (x86_64)

Adobe Flash Player 32-bit installed on Fedora 15 x86_64

32-bit Adobe Flash installed on 64-bit Fedora 15
Adobe Flash Player 32-bit installed on Fedora 14 x86_64

Fedora 14 x86_64 32-bit Adobe Flash Player Installed Firefox 3.6.12
CentOS 5.8 and Red Hat 5.8

Then open following page for real testing Adobe Flash Plugin:
Check is Adobe Flash Plugin Working