Sometimes, a browser like google chrome can't stream/ play youtube videos, if you have IDM, then it keeps ask us to download the videos instead of playing it and the other browser can play the youtube videos. To solve this problem in google chrome:
1. Type 'about:plugins'
3. Open youtube again and it can be played now
4. If the step above still can't play the video, try empty the browser history
5. If still can't play, try open the about:plugins again, then click details on upper right, and disable flash 11.3.31.222
1. Type 'about:plugins'
2. Then check always allowed on flash
4. If the step above still can't play the video, try empty the browser history
