Flash/HTML5 Help

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http://ubuntuforums.org – Hello Ubuntu Forums, I'm running Xubuntu 13.10 [64-Bit] with XFCE 4.10 Desktop. I use Firefox as my web browser, and when I first visited Youtube it asked me to install Flash. The automatic plugin finder popped up, tried to install flash through that but it failed. So I searched the add-ons and installed one that converted Flash to HTML5 and allowed me to watch videos. Sometime today, videos stopped working. It will either display a please update your flash message otherwise tell me my web browser does not recognize any of the available video formats and provides a link for HTML5 Video FAQ. (Hardware)