I use keywords on most of my sites but I don't think they are as important as they once were. My experience seems to indicate that major search engines, Google in particular, are paying a lot more attention to the site content and putting less emphasis on the keyword tag. Of course everybody has a different opinion about this. When I use keywords I place different keywords on each page based on the content of that particular page increasing the chances the search engines will index that particular page the way I want it to be indexed. I don't use keyword phrases such as "teenagers love". I think the individual words are sufficient, but, once again, different folks will give you a different opinion about this.