// Detect whether device supports orientationchange event, otherwise fall back to
// the resize event.
var supportsOrientationChange = "onorientationchange" in window,
    orientationEvent = supportsOrientationChange ? "orientationchange" : "resize";

window.addEventListener(orientationEvent, function() {
    alert('HOLY ROTATING SCREENS BATMAN:' + window.orientation + " " + screen.width);
}, false);

?2.

(function(){
var supportsOrientation = (typeof window.orientation == 'number' && typeof window.onorientationchange == 'object');
var HTMLNode = document.body.parentNode;
var updateOrientation = function() {
  // rewrite the function depending on what's supported
  if(supportsOrientation) {
    updateOrientation = function() {
      var orientation = window.orientation;

      switch(orientation) {
        case 90: case -90:
          orientation = 'landscape';
        break;
        default:
          orientation = 'portrait';
      }

      // set the class on the HTML element (i.e. )
      HTMLNode.setAttribute('class', orientation);
    }
  } else {
    updateOrientation = function() {
      // landscape when width is biggest, otherwise portrait
      var orientation = (window.innerWidth > window.innerHeight) ? 'landscape': 'portrait';

      // set the class on the HTML element (i.e. )
      HTMLNode.setAttribute('class', orientation);
    }
  }

  updateOrientation();
}
var init = function() {
  // initialize the orientation
  updateOrientation();

  if(supportsOrientation) {
    window.addEventListener('orientationchange', updateOrientation, false);
  } else {
    // fallback: update every 5 seconds
    setInterval(updateOrientation, 5000);
  }

}
window.addEventListener('DOMContentLoaded', init, false);
})();

?

(function(){var e=typeof window.orientation=="number"&&typeof window.onorientationchange=="object",f=document.body.parentNode;function c(){c=e?function(){var d=window.orientation;switch(d){case 90:case -90:d="landscape";break;default:d="portrait"}f.setAttribute("class",d)}:function(){f.setAttribute("class",window.innerWidth>window.innerHeight?"landscape":"portrait")};c()}window.addEventListener("DOMContentLoaded",function(){c();e?window.addEventListener("orientationchange",c,false):setInterval(c,5E3)},false)})();

?3.http://davidbcalhoun.com/2010/dealing-with-device-orientation

?