I have a website called DietReviews101. I was ranking on Google on page 1 and 2 for my main keywords. On Saturday I added several new categories and added all my posts to additional categories so I could better categorize them for users. Then today I noticed Google reindexed my site and it has dropped maybe 6 positions or so. Now the permalink structure I use is /%postname%/ so even though my posts are in several categories, it has not created duplicate content as can be the case if you use the /%category%/%postname%/ permalink structure. So my question is, how could adding some categories and making posts into more than one category cause my rankings to drop?