hi shibi you can know more about PR Sculpting at: resource: http://www.jaankanellis.com/what-is-pr-scuplting-and-does-it-work/
It's a strategy to control the way PageRank is passed around within your site. The idea is to ensure that PR only passes to the important / converting pages in your site, and not to unimportant things like contact pages, by making the internal links nofollow. It was fashionable 2 or 3 years ago, but Google recommends against it - http://www.mattcutts.com/blog/pagerank-sculpting/