Video not playing in Firefox on Mac When I open this link Erlang which has a video, the video won't play. I am a beginner to Mac and recently reinstalled my macOS. I dont know why this video won't play on my Mac, but the same video plays in Firefox on another Linux based machine. 

How do I solve this problem?
That is a flash video. You need to install flash for firefox.  https://get.adobe.com/flashplayer/