function center(){
  var x,y;

  if(window.innerHeight){ // IE 외 모든 브라우저
   x = (screen.width - window.innerWidth) / 2;
   y = (screen.height - window.innerHeight) / 2;
  }else if (document.documentElement && document.documentElement.clientHeight) { // Explorer 6 Strict 모드
   x = (screen.width - document.documentElement.clientWidth) / 2;
   y = (screen.height - document.documentElement.clientHeight) / 2;
  }else if (document.body) { // 다른 IE 브라우저
   x = (screen.width - document.body.clientWidth) / 2;
   y = (screen.height - document.body.clientHeight) / 2;
  }
  window.moveTo(x,y);
 }