var isNN = (navigator.appName.indexOf("Netscape")!=-1);
  function autoTab(input,len, e) {
    var keycode = (isNN) ? e.which : e.keyCode;
    var filter = [0,8,9,16,17,18,37,38,39,40,46];
    if(input.value.length >= len && !containsElement(filter,keycode)) {
        input.value = input.value.slice(0, len);
        input.form[(getIndex(input)+1) % input.form.length].focus();
    }
    
  function containsElement(arr, ele) {
    var found = false, index = 0;
    while(!found && index < arr.length)
      if(arr[index] == ele)
              found = true;
      else
              index++;
    return found;
  }
  function getIndex(input) {
    var index = -1, i = 0, found = false;
    while (i < input.form.length && index == -1)
      if (input.form[i] == input)index = i;
      else i++;
    return index;
  }
  return true;
  }