Just as publishers using Google's AdSense can ban certain advertisers from their sites, now advertisers using Googles AdWords can choose to weed out sites on which they don't want their ads to appear, writes JenSense (via AdJab). AdWords users now can add URLs of AdSense publisher websites to a tool called "Campaign Negative Sites,"to stop their ads from appearing on those sites (whether those of competitors or any deemed undesirable).