17 Aug 09 5:36 am
The difference on Ad Group Level and Campaign Level is basically how the negative keyword/s is used or applied by your account. Campaign level setting will set your negative keyword to be active on your campaign, this means to all adgroups. Ad Group level on the otherhand just have your negative keyword on specific ad groups. You may have a campaign in the "Fitness/Diet" market and your adgroups are for different products. Negative keywords may differ for each product because it will depend on the keyword usage of the market.
You can use Negative keywords to filter out the searches that are not relevant to your ad so that people who are not targeted will not see your site. Otherwise it will just be a waste of money for you. Here's what I mean. Example you are in the fitness niche and you are promoting Truth About Abs" product. Say you have a keyword "six pack abs". If you're match phrase is not exact then there might be a possibility that your ad can be seen by people looking for "Six pack" which really meant six pack of beer. In this case you can use "beer" as the negative keyword.