function setBoxPosition() {
  var x;
  if (self.innerHeight) { // all except Explorer
    x = self.innerWidth;
  } else if (document.documentElement && document.documentElement.clientHeight) {
    // Explorer 6 Strict Mode
    x = document.documentElement.clientWidth;
  } else if (document.body) { // other Explorers
    x = document.body.clientWidth;
  }
  lft = x / 2 - 225;
  document.getElementById('container').style.left=lft + 'px';
}