function windowwidth() {
  if (navigator.userAgent.indexOf("MSIE") > 0) w=document.body.clientWidth;
  else w=window.outerWidth;
  return w;
}
function windowheight() {
  if (navigator.userAgent.indexOf("MSIE") > 0) h=document.body.clientHeight;
  else h= window.outerHeight;
  return h;
}
var DHTML = (document.getElementById || document.all || document.layers);
if (DHTML) {
  var obj=document.getElementById("waitDiv");
  obj.style.left=(windowwidth()-waitIMG.width)/2;
  obj.style.top=(windowheight()-waitIMG.height)/2;
}
function ap_getObj(name) { 
  if (document.getElementById) { 
    return document.getElementById(name).style; 
  } else if (document.all) { 
    return document.all[name].style; 
  } else if (document.layers) { 
    return document.layers[name]; 
  } 
} 
function ap_showWaitMessage(div, flag) { 
  if (!DHTML) return; 
  var x = ap_getObj(div); x.visibility = (flag) ? 'visible':'hidden'
} 

ap_showWaitMessage('waitDiv', 1); //แสดงในครั้งแรก