function sb(x) {
  var sb_list = new Array(1,2,3);
  //hide all
  for(var i in sb_list) {
    obj = document.getElementById('sb'+sb_list[i]);
    if(obj != null) {
      obj.style.display = 'none';
      }
  }
  //show
  obj = document.getElementById('sb'+x);
  if(obj != null) {
     obj.style.display = 'block';
  }
}