var myinterval = window.setInterval('randomBackground()', 20000);

function newImage(arg) {
  if (document.images) {
    rslt = new Image();
    rslt.src = arg;
    return rslt;
  }
}

function changeBackground(num, left, top) {
  newImage = "url(http://jibs.keysandwings.com/images/" + num + ".jpg)";
  document.getElementById('bgimage').style.backgroundImage = newImage;
  document.getElementById('bgimage').style.backgroundPosition = left + "px " + top + "px";
}

function randomBackground() {
  var ran_number=Math.round(Math.random()*3+1);
  if (ran_number == 1)
  {
    left_offset = 685;
  }
  else if (ran_number == 2)
  {
    left_offset = 625;
  }
  else if (ran_number == 3)
  {
    left_offset = 660;
  }
  else if (ran_number == 4)
  {
    left_offset = 675;
  }
  changeBackground(ran_number, left_offset, 0);
}

function changeContent(page) {
  frames['contentframe'].location.href='http://jibs.keysandwings.com/' + page + '.php';
}