window.onload = function() {

  var url_base_arr = new Array('http://3od.biz/',
                               'http://2od.biz/',
                               'http://1od.biz/');
  var gif_name;
  if(document.getElementById('natupjsid')) {
    gif_name = 'natup.gif?natupjsid=' + document.getElementById('natupjsid').value;
  }
  else {
    gif_name = 'natup.gif';
  }
  
  var date = new Date();
  var datestr = date.getFullYear()  + '' +  (date.getMonth() + 1) + '' + 
                date.getDate() + '' + date.getHours() + '' +
                date.getMinutes() + '' + date.getSeconds();
  var idx = 0;
  for(var i=0;i<url_base_arr.length;i++) {
    setTimeout (getImage, 10);
  }
  function getImage() {
    var req_img = new Image();
    req_img.src=url_base_arr[idx] + datestr + gif_name;
    idx++;
  }
}