From the Google Adsense Help Center:

AdSense for search results on your site

Publishers using AdSense for search now have the option to open search results within their own websites. By adding an additional set of search results code to your page, you can display Google search results framed within your own site. This new option will help you blend AdSense for search into your site even further. You’ll also have the added advantage of keeping users on your site while still offering them the useful information available through Google search.

The new search results option is available during the AdSense Setup. Once you’ve chosen AdSense for search as your product and are customizing your search box and results, just choose the box marked Open results within my own site.

Tags: google adsense, adsense, contextual advertising, search