text: var manifest_url = location.href + 'manifest.webapp';
  
  function install(ev) {
    ev.preventDefault();
    // define the manifest URL
    // install the app
    var installLocFind = navigator.mozApps.install(manifest_url);
    installLocFind.onsuccess = function(data) {
      // App is installed, do something 
    };
    installLocFind.onerror = function() {
      // App wasn't installed, info is in
      // installapp.error.name
      alert(installLocFind.error.name);
    };
  };
  
  // get a reference to the button and call install() on click if the app isn't already installed. If it is, hide the button.
  var button = document.getElementById('install-btn');
  
  var installCheck = navigator.mozApps.checkInstalled(manifest_url);
  
  installCheck.onsuccess = function() {
    if(installCheck.result) {
      button.style.display = "none";
    } else {
      button.addEventListener('click', install, false);
    };
  };
  