判断设备是否横屏

css3
/* For portrait, we want the tool bar on top */
//横屏
@media screen and (orientation: portrait) {
  #toolbar {
    width: 100%;
  }
}

/* For landscape, we want the tool bar stick on the left */
//竖屏
@media screen and (orientation: landscape) {
  #toolbar {
    position: fixed;
    width: 2.65em;
    height: 100%;
  }

  p {
    margin-left: 2em;
  }

  li + li {
    margin-top: .5em;
  }
}


js

　判断是横屏还是竖屏的方法:
　　function orient() {
if (window.orientation == 90 || window.orientation == -90) {
//ipad、iphone竖屏；Andriod横屏
$("body").attr("class", "landscape");
orientation = ‘landscape‘;
return false;
}
else if (window.orientation == 0 || window.orientation == 180) {
//ipad、iphone横屏；Andriod竖屏
$("body").attr("class", "portrait");
orientation = ‘portrait‘;
return false;
}
}
//页面加载时调用
$(function(){
orient();
});
//用户变化屏幕方向时调用
$(window).bind( ‘orientationchange‘, function(e){
orient();
});

判断设备是否横屏

原文：http://www.cnblogs.com/XIE7654/p/6650521.html