$(document).ready(function(){
  if ($('#launch_chat')) {
    $('#launch_chat').bind('click', function() {
      window.open('include/page.live_chat.php?site_id='+site_id+'&dealer_id='+dealer_id, 'live_chat_session', 'width=500,height=500,toolbar=no,resizable=no');
    });
  }
});