function tabSwitch(new_tab, new_content) {

  document.getElementById('content_1').style.display = 'none';
  document.getElementById('content_2').style.display = 'none';
  document.getElementById('content_3').style.display = 'none';
  document.getElementById('content_4').style.display = 'none';
  document.getElementById(new_content).style.display = 'block';  

  document.getElementById('tab_1').className = '';
  document.getElementById('tab_2').className = '';
  document.getElementById('tab_3').className = '';
  document.getElementById('tab_4').className = '';
  document.getElementById(new_tab).className = 'active';    

}