Today, for adsense ads to be valid, you must add this code between the tags <head> ... </ head>
Code exemple :
<script async src="//pagead2.googlesyndication.com/pagead/js/adsbygoogle.js"></script>
<script>
(adsbygoogle = window.adsbygoogle || []).push({
google_ad_client: "ca-pub-XXXXXXXXXXXXXXXX",
enable_page_level_ads: true
});
</script>
When declaring his domain to google, this code is verified by their robot. If it is not present, you can not advertise.
