Options for Embedded Videos
There are a few options you can choose when embedding a video. These options affect how the video plays.
The first option is to have YouTube display related videos after the embedded video is done playing. You access this option on the YouTube video page itself. Click the Customize This Embed link next to the Embed box, and you see the choices: Include Related Videos or Don’t Include Related Videos. Whichever you choose, the embed code changes to reflect your choice. (By default, YouTube displays the related videos; use this option if you don't want to display any other videos.)
The second option is for whether the video starts to play automatically when your web page loads. By default, it doesn’t; visitors have to click the Play button to view the video. If you want the video to play automatically, you have to insert the following code directly after both instances of the video’s URL in the embed code:
Note that there should be no space before or after this added code.