function opencentered(mypage, myname, w, h, scroll) {
  var winl = (screen.width - w) / 2;
  var wint = (screen.height - h) / 2;
  var winprops = 'height='+h+',width='+w+',top='+wint+',left='+winl+',scrollbars='+scroll+',resizable';
  var win = window.open(mypage, myname, winprops);
  win.window.focus();
  return false;
}

function help(mypage) {
  w = 445;
  h = 540;
  return opencentered(mypage,'help',w , h,'yes');
}

function doOnLoad() {
  if (typeof(onLoad) == "function") {
   onLoad();
  }
}

function showImage(id,start,max) {
  var i=0;
  for (i=start;i<=max;i++) {
    document.getElementById('image_'+i).style.display="none";
  }

  document.getElementById('image_'+id).style.display="block";
}