what about nofollow links ?

Nofollow link is a link that is included on a Web page using standard HTML markup, but contains an attribute to avoid passing link juice or reputation of the destination page. This type of relationship does not improve the link target search engine rankings.

Here is a link to Google followed by the same link with the nofollow attribute added.

Google, Yahoo and MSN have all links nofollow backlink account instead. Google shows only backlinks to select a few for each domain using the operator link from the web interface. Google Webmaster Tools backlinks record include nofollow links, even if they are absent from the operator link.

It is interesting to note that the Google data administrators question number 2:00 indicates that the nofollow attribute is a way to prevent Google from link "Crawling" on a single page.

Google crawl nofollow links but never gives importance to nofollow links but if you will get links on good PR page and having good crawling ration then you keyword will get power in other search engine.

SERP rank means your site position in search results. And this serp directly connected to traffic. As much you get traffic with relevant and quality result then your site be noticed by google. And if google find some meaningful and helpful content on your site then it will show your site in top positions. So get quality traffic and improve the serp rank. So now you may understand that nofollow links can helpful in better serp rank as nofollow links also helpful for getting more traffic.