CSS3에서 @media의 실제 사용에 대한 자세한 설명

@media ：<sMedia> { sRules }

<sMedia>：
    指定设备名称。
{sRules}：
    样式表定义。

media_query: [only | not]? <media_type> [ and <expression> ]*
expression: ( <media_feature> [: <value>]? )
media_type: all | aural | braille | handheld | print | projection | screen | tty | tv | embossed
media_feature: width | min-width | max-width 
| height | min-height | max-height
| device-width | min-device-width | max-device-width
| device-height | min-device-height | max-device-height
| device-aspect-ratio | min-device-aspect-ratio | max-device-aspect-ratio
| color | min-color | max-color
| color-index | min-color-index | max-color-index
| monochrome | min-monochrome | max-monochrome 
| resolution | min-resolution | max-resolution
| scan | grid

@media screen and (max-width: 600px) { /*当屏幕尺寸小于600px时，应用下面的CSS样式*/  
  .class {   
    background: #ccc;   
  }   
}

@media all and (min-width:xxx) and (max-width:xxx){   
/*这段查询的all是针对所有设备(有些设备不一定是屏幕，也许是打字机，盲人阅读器)*/  
}

@media only screen and (min-width:xxx) and (max-width:xxx){   
/*上面针对了所有设备，这段是只(only)针对彩色屏幕设备*/  
}   
device-aspect-ratio

@media only screen and (device-aspect-ratio:4/3)