How to watch older YouTube videos in Higher Quality on YouTube (YouTube HQ hack)

Older YouTube videos may not have "View in Higher Quality" links below them. But by using the following parameter in the URL, you'll be able to watch anything in higher quality (HQ)!

Examples:
Low Quality (LQ) - http://www.youtube.com/watch?v=l5DNZHR0oI8
High Quality (HQ) - http://www.youtube.com/watch?v=l5DNZHR0oI8&fmt=18

How it works:
Just add "&fmt=18" to the end of the URL at the address bar of your web-browser and press the Enter button. That's all! You get Higher Quality YouTube video.

The URL will now look like the following one

http://www.youtube.com/watch?v=l5DNZHR0oI8&fmt=18

And the following YouTube video was made Higher Quality (HQ) by this hack:

If you add "&fmt=22", some YouTube videos are now available at an even higher quality, which makes the full screen view a very useful option. Compare:

http://www.youtube.com/watch?v=l5DNZHR0oI8 (320x180 mono)
http://www.youtube.com/watch?v=l5DNZHR0oI8&fmt=18 (480x270 stereo)
http://www.youtube.com/watch?v=l5DNZHR0oI8&fmt=22 (1280x720 stereo)

All fmt options for YouTube I know:

• Standard: MP3, ~64 kbps, 22.05 KHz, mono (1 channel)
• fmt=5: MP3, ~64 kbps, 22.05 KHz, mono (1 channel) (little difference in video bitrate)
• fmt=6: MP3, ~66 kbps, 44.1 KHz, mono (1 channel)
• fmt=18: AAC, ~126 kbps, 44.1 KHz, stereo (2 channels)
• fmt=22: AAC, ~248 kbps, 44.1 KHz, stereo (2 channels) (it's rare, only if uploaded video have 1280x720)
• fmt=34: AAC, ~68 kbps, 22.05 KHz, stereo (2 channels)
• fmt=35: AAC, ~112 kbps, 44.1 KHz, stereo (2 channels) (it's rare)
• fmt=13 and fmt=17 > only on mobile devices (3GP with AMR or AAC audio)