Websites can create small files/code on user's systems to remember user preferences--these pieces of code are commonly called cookies.
Flash cookies (also known as Local Shared Objects) are a potential privacy concern for internet users even more than standard cookies. For one, Flash cookies cannot be removed they way other cookies can through the browser preference panel. They are stored in a separate folder on your computer. Many users are unaware that Flash cookies even exist. In addition, they cannot be blocked as easily as normal cookies even though they can be used to share information about the user's system with a host. The Mozilla browser does have a way to protect against this technology--but it is an add-on feature.
You can remove Flash cookies from your MAC, Windows (PC), or Linux systems by deleting the files from the following paths:
Windows:
LSO files: “.SOL” extension, all user’s Application Data directory:
Macromedia\Flash Player\#SharedObjects.
Linux:
~/.macromedia
MAC OS:
~/Library/Preferences/Macromedia/Flash Player/
Also, Adobe has created a website to help users remove and manage these files on their systems: https://www.macromedia.com/support/documentation/en/flashplayer/help/settings_manager07.html