If you enjoy the ability to easily start video playback at a specific time using the start parameter, you may also like being able to stop it early. Here’s an example:
<iframe width="420" height="315" src="http://www.youtube.com/embed/Nc9xq-TVyHI?start=110&end=119"
The end parameter is a positive integer, and it represents the number of seconds from the beginning of the video. If your friends are not into merengue dancing canines, you can now tease them with short clips of videos like the one below:
--Jarek Wilkiewicz, YouTube API Team