Google now allow multiple Google-certified ad networks to compete for display ad space on AdSense enabled sites. With this new change, participating ad networks can also bid in auction to appear on AdSense sites. This new capability’ll help you generate the most profit for every ad that appears on your site, whether the ads come from AdWords advertisers or Google-certified ad networks. As new networks are certified, you'll see them appear in your account. You'll have control over which networks can show ads on your pages, can choose to opt out of receiving ads from specific networks, or all networks completely, or continue to show ads from only AdWords advertisers if you like. This feature’ll initially be available to North America and Europe publishers.