Google announced on the AdSense blog a new "quality effort" they are rolling out. Before you can earn money from ads you place on web sites, you need to first add them to your verified sites section in AdSense and Google has to verify them.
Google said that "before you can show ads on a new site, you now have to add the site to your AdSense account." Google will then take that site "through a verification process which checks that you own the domain or have the ability to modify its content." During this verification process, Google will also review the site for compliance with the AdSense Program policies.
If all is good and all the "checks are completed", your site will be marked as "Ready" and you can start showing ads.
You can verify sites by going to your AdSense account, click sites under settings, click Add site and then enter the URL of your site.
Google said this will have a minimal impact on most AdSense publishers, they wrote:
For the vast majority of AdSense users, the only change will be the new Sites tab. However, for some of you, we may ask for help to find the correct ad code when you add a new site. If we require your help, we’ll reach out through email and notify you when you sign in to AdSense. So don’t forget to make sure we have the correct email address for you and that your email preferences are up to date.
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