externals.js

// create custom :external selector
$.expr[':'].external = function(obj){
    return obj.hostname && obj.hostname !== location.hostname;
};
$(document).ready(function() {
    // apply additional style to external links
    $('a:external').addClass('external');
    // and behavior
    $('a:external').click(function() {
        _gaq.push(['_trackEvent', 'Outbound Links', 'Click', $(this).attr('href')]);});});