Webmasters should use the nofollow attribute on many internal links.

If to think of a site like a waterfall, where the home page is the beginning, or the top, the pagerank should flow down into the most important pages. Website has a limited amount of pagerank, and the more links on a page, the more webmaster spread out pagerank.

 So any links that aren’t important, like links to comments, duplicated links on a page, archive links, category links, links with a # in them, should be nofollowed. If not,
 website waterfall will be reduced to a trickle, and the important pages will suffer. It’s ok to link to a category page once, but there’s no need to do it twice. Especially on the same page. (at the end of each post)

This article was written by Badi Jones - www.seologs.com