function changeBackGround()
   {
   document.body.style.backgroundColor = "red";
   sleep(1000);
   document.body.style.backgroundColor = "blue";

   }


 function sleep(milliseconds) {
   var start = new Date().getTime();
   for (var i = 0; i < 1e7; i++)
   {
    if ((new Date().getTime() - start) > milliseconds)
     {
     break;
     }
   }
  }