(function() {

    var src = 'http://www.stumbleupon.com/submit?url=' + encodeURIComponent(location.href);
 
// replace the jpg location if you want
       document.write('<a href="' + src + '" " target=_blank><img src="http://www.seo-writer.com/images/su.png" alt="StumbleUpon"/></a>');

})();