Negative Keywords are keywords you do not want your ad to show for when in combination with other phrases which may or may not be relevant. They are highly important to your campaign’s success. Without them you may be showing your ads for irrelevant queries, spending money on irrelevant clicks, and dealing with a lower click-through rate than you deserve. When working with large or highly stratified accounts, adding negative keywords on the adgroup level can be tedious. Using the AdWords Editor, there is a way to quickly add account-wide negative keywords.
I’ve done this many times and it always increase click-through rates as well as conversions. Some common negative keywords you typically always want to add if you are selling products or services are: free, pro-bono, pictures, photos, and history of. Depending on your industry you could have 100s more negative keywords which are often associated with your true keywords, but are not associated with someone in the buying mode. Or by adding one of these words, it could completely change the meaning of the product or service. If you need help finding your negative keywords here is a quick guide I wrote a while back with some excellent examples on SEOChat — Building Your Negative Keyword List – Three Progressive Strategies.

I’ll get back to the subject at hand. Hiren, over at over SEOAddicted.com does a through job of explaining how to add account-wide negative keywords.

I will let him take it from here, since he has already taken the time to explain. Read How to quickly add Account wide Negative Keywords here.