adCenter recently increased their negative keyword limits to ‘thousands.’ This is great news for those who have been optimizing their campaigns in preparation for the Yahoo search marketing and adCenter merger. Previously, advertisers were able to only add less than a 150 negative keywords. To start taking advantage of the new system capability, go to your campaign or ad group settings and add new exclusions.
Unfortunately, unlike with AdWords, in adCenter negative keywords still cannot be assigned a match type. If you’re curious about when you might want to assign different match types to your negatives, and want to read more about negative keywords, see my post on negative keyword best practices.