Edit in JSFiddle

/*
* Async Sharing Buttons (G+, Facebook, Twitter)
* http://www.narga.net/load-social-button-javascript-asynchronously/
* Simple JavaScript function that loads the third-party scripts asynchronously and after the page loads to improve site performance.
*/
(function(doc, script) {
    var js, fjs = doc.getElementsByTagName(script)[0],
        frag = doc.createDocumentFragment(),
        add = function(url, id) {
            if (doc.getElementById(id)) {
                return;
            }
            js = doc.createElement(script);
            js.src = url;
            id && (js.id = id);
            frag.appendChild(js);
        };

    // Google+ button
    add('http://apis.google.com/js/plusone.js');
    // Facebook SDK
    add('http://connect.facebook.net/en_US/sdk.jsxfbml=1&version=v2.3', 'facebook-jssdk');
    // Twitter SDK
    add('http://platform.twitter.com/widgets.js');

    fjs.parentNode.insertBefore(frag, fjs);
}(document, 'script'));

<a href="https://twitter.com/share" class="twitter-share-button" data-count="horizontal" data-url="http://www.narga.net">Tweet</a>

<div class="g-plusone" data-size="medium" data-count="true" data-href="http://www.narga.net/"></div>

<div id="fb-root"></div>
<div class="fb-like" data-send="false" data-layout="button_count" data-width="1" data-show-faces="false" data-href="http://www.narga.net/"></div>