Components.utils.import('resource://gre/modules/Microformats.js');

var doc = Application.activeWindow.activeTab.document;

var hCards = Microformats.get('hCard', doc.documentElement);
hCards.forEach(function(card) {
  alert([
    'Name: '+card.fn,
    'E-mail: '+card.email.value,
    'Country: '+card.adr['country-name']
  ].join('n'));
});

hCards = Microformats.get('hCard', doc.documentElement,
  { showHidden : true }, hCards);