function addLoadEvent(func) {
  var oldonload = window.onload;
  if (typeof window.onload != 'function') {
    window.onload = func;
  } else {
    window.onload = function() {
      if (oldonload) {
        oldonload();
      }
      func();
    }
  }
}

addLoadEvent(function() {
    rotater();
})

var imgWrapper = document.getElementById("imgrotate");
var imgs = imgWrapper.getElementsByTagName("img");
var randomnumber=Math.floor(Math.random()*imgs.length)    
    //alert(imgs.length);
    function rotater() {   
	    //alert(imgs.length);
	    imgs[randomnumber].className = "show";
    }