It is NOT AT ALL recommended to install Flash Player 11.3, especially on internet connected systems. 11.3 was released the summer of 2012 - almost 6 years ago. It contains security exploits that have been fixed in subsequent versions of Flash Player. Adobe always recommends installing/running the latest version of Flash Player, and most modern browser's will not allow old versions of Flash Player to run. If you're attempting to view content that states something along the lines of "this content requires Flash Player 11.3" you should install the latest version, not 11.3. If you 'need' to install 11.3, it's available on the Archived Adobe Flash Player versions page.