use some seo plugin like - All in One SEO or Platinum SEO??

they give you the option to add noindex, nofollow etc for each post... you can select that if you dont want them to be indexed...
Rox Reviewed by Rox on . How To add no follow tag to individual posts in wordpress? hello guys as title says i have a wordpress blog with 1600 posts i wanna add nofollow tag for 20 posts each one has 25 thumbnails to some imagehosting site Rating: 5