This short tutorial is going to show you how to install Adobe Flash Plugin on Debian 7.5 Wheezy. By installing this Adobe Flash Plugin, you can then play YouTube and any other online video from your web browser such as Firefox, Google Chrome on Debian system. By default, you wont be able to install Adobe Flash Plugin on Debian 7.5 unless you have the following line in your /etc/apt/sources.list.
deb ftp://ftp.debian.org/debian stable main contrib non-free
So, you will need to edit the /etc/apt/sources.list
sudo nano /etc/apt/sources.list
Add the following line to it
deb ftp://ftp.debian.org/debian stable main contrib non-free
Now update
sudo apt-get update
Install Flash Plugin
sudo apt-get install flashplugin-nonfree
Now check if Adobe flash plugin is installed correctly. Open Firefox and type "about:plugins" without quotes. You should see Shockwave Flash listed there.