Currently, this site embeds YouTube videos as Flash. (see an example: Hidden areas in Portal 2 single player campaign?)
However, this is not the best solution, as now YouTube also supports HTML5, and some users (like me!) prefer to use HTML5 player instead of Flash. Supposedly, it should also work on devices that don't have Flash player (I can't confirm because I don't have one).
The solution seems quite simple: just change the embed code to an
iframe, as described at A New Way To Embed YouTube Videos