function externalChartHandler(user_id, url) {  
  var outputHTML = '<a href="http://voomaxer.com/users/'+user_id+'">';
  outputHTML += '<img id="voomaxer_chart_image" src="'+url+'" alt="Voomaxer.com" />';
  outputHTML += '<br /><img id="voomaxer_static_chart_footer" src="http://voomaxer.com/images/static_chart_footer.png" alt="Voomaxer.com" />'; 
  outputHTML += '</a>';
  
  document.getElementById('voomaxer_chart_'+user_id).innerHTML = outputHTML;
}