Updated: Disable 60p High Frame Rate Mode On YouTube (Revert To 30p)
The method for disabling 60p playback mode on YouTube described in an earlier video of mine, while still working, is no longer an optimal solution due in large part to the necessity of reverting to using Adobe Flash Player just to revert to 30p.
Using the plugin for both Firefox and Google Chrome called "YouTube Plus," short work is made of reverting to 30p playback on videos whose only HD playback options, by default, are in 60p. Unlike the previous workaround I detailed, this plugin can disable 60p on either the HTML5 or Adobe Flash players.
Reverting to 30p proves useful when your computer or internet connection can otherwise handle HD video just fine so long as it isn't 60p!