How to check if a site is do-follow or no-follow?

Everyone who owns a website or blog is concerned about SEO,and getting quality back-links from all over the web is an equally important part of "Search engine optimization".and more over links from "do-follow" site means improving your ranking.So here is the question,        "How do i find if a site that is linking to mine is having do follow or no follow attribute"Find this is not a difficult