I wondered and couldn't satisfied yet. How much i know i think link with no follow attribute are worth useless.They just can help in bringing a visitor not a crawler to our site but as some of the seo professional suggested me to concentrate them coz they help to put the site high in SERP. I am confused what to do as i have done blog commenting on most relevant theme related blogspots and most of them are with no follow attribute linking back to my site. No doubt i have gain improvment in my sites ranking but i am not sure because along with blogspot commenting i have done forum posting and directory submission as well. So what you people think that in this improvement have i got any kind of help from the backlinks with no follow attribute especially from the blogspot.