You Tube doesn't have a setting to set the default resolution of the video. Thus, to set it to a default resolution we can use different plugins (extensions) for different browsers listed below:
1. Firefox Plugin:
SmartVideo For YouTube (My Tube)
2. Chrome Extension:
YouTube Quality Selector
Note: This extension works only with the Default Player, and not on Channel Pages, Embedded Players and HTML5 players.
3. Opera Extension:
ExtendTube
Have Fun! Cheers...
1. Firefox Plugin:
SmartVideo For YouTube (My Tube)
2. Chrome Extension:
YouTube Quality Selector
Note: This extension works only with the Default Player, and not on Channel Pages, Embedded Players and HTML5 players.
3. Opera Extension:
ExtendTube
Have Fun! Cheers...