WATCH HIGH RESOLUTION VIDEOS BY SIMPLY EDITING YOUTUBE LINKS

Youtube videos are usually in 320x240 Mono format. But if you want you can change the format.

To increase the resolution, you have to append "&fmt=" with youtube links.
Let me show :

If youtube link is:

http://www.youtube.com/watch?v=9kCinKpY2MM

Then change it to :

http://www.youtube.com/watch?v=9kCinKpY2MM&fmt=22

Notice that after   &fmt=  I have added a digit 22.

The trick is you can put number as your wish. 

• &fmt=6 is for 448x336, Flash 7 video-900Kbps; audio - 44.1KHz 96Kbps Mono CBR 
• &fmt=18 is for 480x360, H.264 video - 512Kbps; audio - 44.1KHz 128Kbps Stereo 
• &fmt=22 is for Maximum 1280×720 (720p), H.264 video - 1024Kbps; audio - 44.1KHz 232Kbps Stereo

You can use &fmt=24 for ultra higher resolution than these if any other higher resolution videos remain available.