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Disclaimer: I do not believe this is in accordance with Google's AdSense terms of service, be warned.
A thread at DigitalPoint Forums describes how you can realize a 500% Increase in revenue from Search. Basically what the AdSense publisher did was pre-populate a keyword within the Google Adsense search box.
Is this legal? Probably not, since you are not allowed to modify the AdSense code in any way.
