One nightmare problem across operating systems and device platforms (including Gnu/Linux) is; world wide web pages being created with incompatible browser plug-ins to the device trying to view it. That is the majority of plug-ins only being made to work on Microsoft's Windows and Apple's Macintosh (? whatever an Apple is called nowadays). Reading that statement some people may say "Who cares. Nobody uses (Gnu/)Linux.", however they would be forgetting the amount of other devices that can browse the web nowadays, including (but not limited to); Android, BSD, PlayStation consoles, Xbox consoles, iDevices, and Chromebooks.
Common Browser Plug-ins
Three of the, probably, most used plug-ins are:- Adobe Flash Player - used by many sites to display video and other sites to watch flash animations and play flash games.
- Shockwave Player - not really used since the 90s (:P) and mainly used to play shockwave games.
- Unity3D - a somewhat new player to the table for 3D games, and despite Unity3D SDK being able to compile games to Linux, there is no native Linux web browser plug-in.