Some months ago Matt Cutts informed us that PageRank Sculpting is not possible any more by using the rel=nofollow attribute. Nofollow method is straightforward and time efficient comparing to other methods such as iframes, javascript, Java, flash etc. An other problem is that the sites that already use nofollow might suffer a PR loss.

Using rel=nofollow for PageRank sculpting is still possible by using a special free Javascript/PHP script. What is does is that just before the HTML code is sent to the user, it scans for nofollowed links and it replaces them with obfuscated javascript, post requests etc. The URLs are encoded and they can not be detected by Google.

This script has been tested for more than 3 months and it seems it works very good with all the browsers.

You can download the script, find installation instructions and more info about how it works in this site:
http://www.webseoanalytics.com/blog/pagerank-sculpting-you-can-still-use-nofollow/

Although in the SEO world it feels like a lifetime ago since nofollow appeared, it's actually only been around since January of 2005, when Google announced it was adopting support for the new HTML tag.

Very simply, rel="nofollow", when attached to a link, tells the engines not to ascribe any of the editorial endorsements or "votes" that would boost a page/site's query independent ranking metrics.