For those who don’t know what no-follow and do-follow backlinks are: There is a theory that backlinks are of two kinds. First one is Dofollow backlinks and the second one is Nofollow backlinks. Actually there is no tag like a dofollow backlink but whatever backlinks that are nor nofollow are considered to be dofollow backlinks. The no-follow backlinks thing was brought into the industry by Google search engine a couple of years ago probably because it was fed up with all the spam links it had to deal with daily and decided to put an end to the growing spam. So it coined the nofollow thing and stated whatever backlinks are tagged nofollow (any links, for example blog comment links, forum signature links, article directory links, social bookmarking links etc) are not counted as backlinks in determining the SERP rank of your site for a particular keyword.
And since the big daddy G Google itself implemented this strategy in ranking sites in the search engine results pages, the remaining two major search engines Yahoo and Bing (MSN aka Live) are said to value the no-follow tag and don’t count the no-follow links in ranking for a search query. According to Google search engine, once a link is tagged as no-follow on a site the search engine won’t even look which website’s link that is. So as soon as it see the nofollow tag before the link, it doesn’t even bother checking if that link belongs to famous sites like CNN, Microsoft, or even Google itself or any other newly started nobody website. Or do Google actually identify which website’s link that is but discount them from the backlinks list which affect the ranks of a website in a positive or negative way (I hear that some backlinks can hurt your rankings, especially links from @dult sites and spam sites).
So, Now it is up to us to check whether Google and the other two search engines (Yahoo, Bing) really discount nofollow backlinks or whether they would count them in rankings but with less importance. Like the same way you test most of the SEO assumptions, tips, tactics, theories and strategies you need to register a random (with no particular keyword in mind, example bsdkndiprt.com) domain (.com is preferred but if you want to test in country specific search engines too, go ahead and register some random .co.uk and .in CCTld domains) and post an article with a length of 500 to 1000 words without our testing keyword anywhere in the article, be it is title or body or tags or even comments and get a bunch of no-follow links with a keyword say “Testing nofollow” as anchor text and wait for a couple of days or weeks and see if your site ranks anywhere in the SERPs for the kwyword “Testing nofollow”. I think you got the point of this SEO test. If your site doesn’t show up anywhere in the serps for the particular keyword even after two three months, you can then assume nofollow links can’t affect your rankings. But, on the other hand, if your site comes up in search engine results for that keyword, then you may think even the no-follow links affect your rankings in serps.
But with this kind of tests you can’t be really sure about the outcome be it positive or negative. It is because rankings depend on many other factors and you should keep every aspect in mind before conducting a test like this. Also, when you test this kind of tests you should always choose a very low competed keyword like “Testing nofollow”. It is because if you chose “Web Hosting” or “SEO” kind of very high-competed keywords for the test, because of the sheer amount of competition even if your site comes up on the 100th or even 1000th (LOL) page with only those no-f0llow links, you might not notice your domain in the SERPs (even with serp ranking tools, they are not perfect anyways) and assume the wrong result as the outcome. In such cases the purpose of the test is defeated. So, always choose a very low competed keyword as an anchor text for nofollow links (in this case) and make sure you never use that keyword on your website. Happy testing!