js广告代码怎么添加进网页

<div class="ad_300_100">
	<script type="text/javascript">
		 //淘宝的广告代码，就是这样放的
		 document.write('<a style="display:none!important" id="tanx-a-mm_43439014_7536100_25124355"></a>');
		 tanx_s = document.createElement("script");
		 tanx_s.type = "text/javascript";
		 tanx_s.charset = "gbk";
		 tanx_s.id = "tanx-s-mm_43439014_7536100_25124355";
		 tanx_s.async = true;
		 tanx_s.src = "http://p.tanx.com/ex?i=mm_43439014_7536100_25124355";
		 tanx_h = document.getElementsByTagName("head")[0];
		 if(tanx_h)tanx_h.insertBefore(tanx_s,tanx_h.firstChild);
	</script>
</div>