function callActionTag(tag) {
  var valid_tags = $w('astusa_UnscrewLandingPage_1 astusa_EmailSignUpButton_1 astusa_EntertheTopHalfoftheSite_1 astusa_PayPalDonationsButton_1');
  var base_url = 'http://switch.atdmt.com/action/';
  var tracking_image = $('action_tag');

  if (valid_tags.include(tag)) {
    valid_tag = base_url + tag;
    if (tracking_image.writeAttribute('src', valid_tag)) {
      console.log('action tracked!');
    } else {
      console.log('there was an error tracking the action.');
    }
  } else {
    console.log('invalid action tag!');
  }
}

Event.observe(window, 'load', function() {
  callActionTag('astusa_UnscrewLandingPage_1');
});