Given the improvements in our technology to more accurately match ads with your content and users, the section targeting feature from our early days is now obsolete. This means that there's no longer any need for you to implement section targeting in order to help us determine which parts of your content are important.
For more information on AdSense’s available targeting methods, visit how ads are targeted to your site.
If you'd like to see how ads are being targeted to your site, we recommend running the Targeting types report. To run this report, visit the Performance reports tab in your AdSense account and select Targeting types in the left-hand panel.