var bgimg;
var init = function() {
  if (arguments.callee.done) return;
  arguments.callee.done = true;
  bgimg = document.getElementById('bgimg');
  if (!bgimg) return;
  bgimg.onload = resizeBg;
  bgimg.src = bgimg.src;
  if (window.addEventListener) window.addEventListener('resize', resizeBg, false);
  else if (window.attachEvent) window.attachEvent('onresize', resizeBg);
  else window.onresize = resizeBg;
}
var resizeBg = function() {
  var w = self.innerWidth || document.documentElement.clientWidth;
  var h = self.innerHeight || document.documentElement.clientHeight;
  //window.status = w + ' ' + h;
  if (bgimg.width !== w) {
    bgimg.parentNode.style.left = '0';
    bgimg.parentNode.style.top = '0';
    bgimg.height = (w / bgimg.width) * bgimg.height;
    bgimg.width = w;
  }
  if (bgimg.height < h) {
    bgimg.width = (h / bgimg.height) * bgimg.width;
    bgimg.height = h;
    bgimg.parentNode.style.left = '-' + ((bgimg.width - w) / 2) + 'px';
  }
  else if (bgimg.height > h) {
    bgimg.parentNode.style.top = '-' + ((bgimg.height - h) / 2) + 'px';
  }
}

if (window.addEventListener) window.addEventListener('load', init, false);
else if (window.attachEvent) window.attachEvent('onload', init);
else window.onload = init;