function toggle_trial() {
    var e = document.getElementById('trial-tab');
    var f = document.getElementById('trial-button');
    if(e.style.display == 'block') {
       e.style.display = 'none';
       f.style.backgroundPosition = '0 1px'; }
    else {
       e.style.display = 'block';
       f.style.backgroundPosition = '0 bottom'; }
   }