function centermainlayer() {
    var mainstyle=document.getElementById("outer").style;
    newleft=Math.abs(document.body.clientWidth/2)-400;
    mainstyle.left=newleft+"px";
    if (newleft<20) {
      document.bgColor="#f5f5f5";
    }
    else {
      document.bgColor="#ffffff";
    }
  }
  window.onresize=centermainlayer;