View youtube videos in 720p by default in Safari? Is there a way I can force safari to start youtube videos at 720p by default ?? I was wondering if there is an automator code that can achieve this ? Or maybe an extension that solely does that ? (I have found an extension that controls your youtube or whatever but I prefer something that only has one feature).

Although I have the settings already activated as the first answer suggested, I still have that problem.
There should be an option in your Youtube settings to default to HD resolutions if they're available. It should be under Playback Settings>Video Playback Quality.