如, 原来的代码是
<!--CNZZ统计 开始 -->
<script type="text/javascript">
var cnzz_protocol = (("https:" == document.location.protocol) ? "https://" : "http://");
document.write(unescape("%3Cspan id='cnzz_stat_icon_123333397'%3E%3C/span%3E%3Cscript src='" + cnzz_protocol + "s23.cnzz.com/z_stat.php%3Fid%3D123333397%26online%3D2' type='text/javascript'%3E%3C/script%3E"));
</script>
<!--CNZZ统计 结束 -->
更改后的异步代码是
<!--CNZZ统计 开始 -->
<span id='cnzz_stat_icon_123333397'></span>
<script>
var cnzz_protocol = (("https:" == document.location.protocol) ? "https://" : "http://");
var cnzz_s_tag = document.createElement('script');
cnzz_s_tag.type = 'text/javascript';
cnzz_s_tag.async = true;
cnzz_s_tag.charset = 'utf-8';
cnzz_s_tag.src = cnzz_protocol + 's23.cnzz.com/z_stat.php?id=123333397&online=2';
var root_s = document.getElementsByTagName('script')[0];
root_s.parentNode.insertBefore(cnzz_s_tag, root_s);
</script>
<!--CNZZ统计 结束 -->