function parallax(e) {
  // Get the width and left-margin of div id="Frame" and determine it's center.
  var obj = document.getElementById('Frame');
  var objW = obj.offsetWidth;
  var posX = obj.offsetLeft;
  while(obj.offsetParent){
	posX=posX+obj.offsetParent.offsetLeft;
		  if(obj==document.getElementsByTagName('body')[0]){break}
		else{obj=obj.offsetParent;}
  }
  var center = posX+objW/2;

  // Get the horizontal mouse position.
  var tempX = 0;
  e=e||window.event;
  if (e.pageX) {
    var tempX = e.pageX;
  } else if (e.clientX) {
    var tempX = e.clientX + document.body.scrollLeft + document.documentElement.scrollLeft;
  } else {
    return false; //browser doesn't work
  }

  // Store div id"BgOne"-"BgEig" in Array 'ids'. Loop 8x for each div's new relative left-margin position.
  var div, num;
  var ids=['BgOne', 'BgTwo', 'BgTre', 'BgFou'];
  for(var i=0;i<4;++i) {
    div=tempX*(i+1)/10;
    num=center-center*(i+1)/8;
    document.getElementById(ids[i]).style.left=div-center+num+"px";
  }
}