window.onload = function changeBG () {

var backgroundArray= new Array();

 backgroundArray[0] = "img/backgrounds/Margo_8.jpg";
 backgroundArray[1] = "img/backgrounds/Margo_8.jpg";
 backgroundArray[2] = "img/backgrounds/Margo_8.jpg";
 backgroundArray[3] = "img/backgrounds/Margo_8.jpg";
 backgroundArray[4] = "img/backgrounds/Margo_8.jpg";
 backgroundArray[5] = "img/backgrounds/Margo_8.jpg";

 randBG = Math.floor(Math.random( )*backgroundArray.length);
 var fullURL = "url(/"+backgroundArray[randBG]+")";
 document.body.style.backgroundImage = fullURL;
}

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()
 {
 document.getElementById("loading").style.display="none";
 }
);