Wrong return value for 'canPlayType'

[mycroes]

the canPlayType function returns "no" if the expected result is that the src file can not be played. However, the string "no" evaluates to the boolean true, and thus this has been changed in HTML5 so that the empty string is returned instead. Also, it would be nice if these were defined as constants somewhere in the code, which would make any future changes easier...

[trieloff]

Good point, I missed that change, but it makes sense.