prevent people from using your adsense code

AdSense have added a new ‘Allowed Sites' feature to the back end of their system for publishers to use. By using this feature publishers have more control over their Adsense accounts.

To use this feature logging into your AdSense account and click on AdSense Setup and then the Allowed Sites and choose the radio button (Only allow certain sites to show ads for my account).

Allowed sites are sites or URLs on which AdSense publishers allow or wish to have their Google ads displayed. If a URL displaying your AdSense ad code is not on your Allowed Sites list, ads will still be displayed, but impressions and clicks won't be recorded, advertisers won't be charged, and you won't receive any earnings for that URL.