from http://code.google.com/p/aframework/source/browse/trunk/__core/Modules/Base/jquery.favicons.js

gistfile1.js

/**
 * Favicons 1.0.th
 *
 * Prepends or appends a favicon image to all external links
 *
 * Usage: jQuery.favicons();
 * 
 * @class favicons
 * @param {Object} conf, custom config-object
 *
 * Copyright (c) 2008 Andreas Lagerkvist (andreaslagerkvist.com)
 * Released under a GNU General Public License v3 (http://creativecommons.org/licenses/by/3.0/)
 *
 * Travis's Changes:
 * - Updated filter for external links using http://www.learningjquery.com/2008/08/quick-tip-dynamically-add-an-icon-for-external-links
 * - Customized config
 * - Extended for https support
 * - Configurable ALT text
 */
jQuery.favicons = function(conf) {
	var config = {
		insert: 'append', 
		defaultIco: '/images/external.png',
		alternateText: 'external site icon'
	};

	config = jQuery.extend(config, conf);

	jQuery('a[href]').filter(function() {
			return this.hostname && this.hostname !== location.hostname;
		}).each(function() {
			var $link = jQuery(this);
			var faviconUrl = $link.attr('href').replace(/^(https?:\/\/[^\/]+).*$/, '$1') +'/favicon.ico';
			var $faviconImg = jQuery('<img src="' + config.defaultIco +'" alt="' + config.alternateText +'" />')[config.insert +'To']($link);
			var extImg = new Image();

			extImg.src = faviconUrl;
			if(extImg.complete) {
				$faviconImg.attr('src', faviconUrl);
			}
			else {
				extImg.onload = function() {
					$faviconImg.attr('src', faviconUrl);
				};
			}
		});
};