function goBack() {
  history.go(-1);
}

function toggleDisable(id) {

  var checked = false;

  if (id == 'item1') {
    if ($('item1').checked) {
      $('item2').checked = false;
      $('item2').disabled = true;
    } else {
      $('item2').disabled = false;
    }
    return;
  }

  $$('.hasDownload').each(
    function(item) {
      if (item.checked == true) {
        checked = true;
      }
    }
  );

  if (checked == true) {
    $$('.downloadOnly').each(
      function(item) {
        item.checked = false;
        item.disabled = true;
      }
    );
  } else {
    $$('.downloadOnly').each(
      function(item) {
        item.disabled = false;
      }
    );
  } 
}

function validateOptions() {
  var options = $('options').select('input[type="checkbox"]');

  var checked = false;

  options.each (
    function (o) {
      if (o.checked == true) {
        checked = true;
      }
    }
  )

  if (checked == false) {
    $('error').update('You must make a selection in order to proceed.'); 
    return false;
  } else {
    $('optionsForm').submit();
  }
}