html5媒體屬性問題

Question

這兩個媒體屬性值是否意味着下面同樣的東西？如果不是什麼意思？它們都有效嗎？

<source src="music.mp3" media="screen, (color)"> 
<source src="music.mp4" media="screen and (color)"> 

Answer 1

http://dev.w3.org/csswg/css3-mediaqueries/

他們是不等價的。逗號表示OR，而不是AND。查詢中的and表示測試的兩側必須是真實的才能匹配。即：

screen, (color) = is a screen or anything that supports color 
screen and (color) = is a color screen 
projection, screen and (color) = is any type of projector OR a color screen