Измените Favicon с JavaScript
(function() {
var link = document.querySelector("link[rel*='icon']") || document.createElement('link');
link.type = 'image/x-icon';
link.rel = 'shortcut icon';
link.href = 'http://www.stackoverflow.com/favicon.ico';
document.getElementsByTagName('head')[0].appendChild(link);
})();
wiichicken