function backToTop() {
  var x1 = x2 = x3 = 0;
  var y1 = y2 = y3 = 0;
  if (document.documentElement) {
      x1 = document.documentElement.scrollLeft || 0;
      y1 = document.documentElement.scrollTop || 0;
  }
  if (document.body) {
      x2 = document.body.scrollLeft || 0;
      y2 = document.body.scrollTop || 0;
  }
  x3 = window.scrollX || 0;
  y3 = window.scrollY || 0;
  var x = Math.max(x1, Math.max(x2, x3));
  var y = Math.max(y1, Math.max(y2, y3));
  window.scrollTo(Math.floor(x / 2), Math.floor(y / 2));
  if (x > 0 || y > 0) {
      window.setTimeout("backToTop()", 25);
  }
}

function navControl(code){
  if (! document.getElementById) return;
  document.getElementById("globalNav").className = "part" + code;
}

function preload(imgs){
 for(var i = 0; i < imgs.length; i++){
   var imgObj = new Image();
   imgObj.src = imgs[i];
 }
}

preload(["http://www.hisai-ig.com/_common/images/bgGlobalNav1.jpg", "http://www.hisai-ig.com/_common/images/bgGlobalNav2.jpg", "http://www.hisai-ig.com/_common/images/bgGlobalNav3.jpg", "http://www.hisai-ig.com/_common/images/bgGlobalNav4.jpg"]);