function divMiddle(){
 var dairyBox = document.getElementById('dairyBox');
 var divHeight = dairyBox.offsetHeight;
 var bodyHeight = document.body.offsetHeight;
 if(bodyHeight > divHeight){
  var endHeight = parseInt(bodyHeight - divHeight)/2;
  dairyBox.style.marginTop = endHeight + "px";
 }else{
  dairyBox.style.marginTop = 0;
  dairyBox.style.top = 0;
 }
}
            
if(document.all){
 window.attachEvent('onload',divMiddle);
}else{
 window.addEventListener('load',divMiddle,false);
}
             
var resizeTimer = null;
window.onresize = function(){
 resizeTimer = resizeTimer?null:setTimeout(divMiddle,0);
}