Google is launching a new feature Friday that lets publishers of AdSense partner Web sites sign up advertisers on their own. Under the new Onsite Advertiser Sign-up, marketers can create site-targeted ads and submit cost-per-impression bids on the targeted site. Previously, advertisers had to go to Google's Web site to do that. With AdSense, Web publishers agree to run text and banner ads brokered by Google and share per-click revenue with the company. Google's contextual ad-matching technology is designed to ensure the ads are relevant to the site's content.