Google custom search engine!
If you have Google search on your site, you can now customize its behavior! You can specify a list of sites to search and a list of keywords that is of high priority to your sites. This means that search users in your site will see what you want them to see! This also should help in getting more targeted ads and more adsense revenue.
From the Google adsense blog,
1. Visit http://www.google.com/coop/cse/ and select the websites you’d like to include in your search index.
2. Then choose to restrict search results to include only those pages and sites, or you can give those pages and sites higher priority and ranking within the larger Google index when people search on your search engine.
3. From the CSE site, you can generate the code to place on your site and make the search engine, through an IFRAME, look and feel like your own. If you choose, you can easily link to your current AdSense account so you have a centralized place to manage your Google AdSense relationships.
4. Last but certainly not least, you can invite members of your community to contribute to your search engine index, in real time. Simply enter email addresses of people you’d like to contribute and an invitation along with Google Marker will be sent to your invitees.
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