TED Video Streaming – Choose Video Quality in TED Online Player

Seems that the best YouTube supports is specifying that you want HD (720p) if available. That's accomplished by appending &hd=1 to the URL.

Almost a year ago, someone asked pretty much the same question on the YouTube support forum and got "Thanks for bringing this to our attention; we are looking at how to resolve this, and I will update you accordingly." from a Google employee, but I can't find any evidence that a fix has been released since then.

There are two option available to play the youtube video and you need to select one

(i) Always choose the best quality for my connection and player size

(ii) I have a slow connection. Never play higher-quality video

This can be seen in the setting page by going to settings -> playback and it is applicable for globally.

If you have chosen the 1st option,then video would be played in hd mode.

There is choice in the playing video you have option to chose the pixel size.This is saved temporarily so if you refresh it would revert back to the default option and your selection would be unchecked so this is reason why it went back to 1080 p since you have select the 1st option.