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So, even links from no follow coded pages can appear in Yahoo’s backlink index, as those links are actually being followed by search engines. I’ll also go out on a limb to say that the aspect of the no follow link is a bit outdated when it comes to search indexing & ranking, as even if those links don’t pack “ranking juice”, they will help to define you and your site’s:
* online reputation
* profiles of users who visit your site and sites they have visited in the past
* clustering of similar pages and content
* and identifying links to pages which may have not had SEO in mind when obtaining those links or contributing to such discussions.
Such variables, included in a new age algo (and some in published Google & Yahoo patent apps), sound quite revelant to me, even if those links have no “PageRank” or “SiteRank” juice.
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What Nofollow Means
Below I'll cover what Google says it does, if it sees a link with the nofollow attributed associated with it. Yahoo and MSN are likely to react in a similar fashion, though I haven't yet spoken with them to get exact details since news of their support only just emerged.
If Google sees nofollow as part of a link, it will:
NOT follow through to that page.
NOT count the link in calculating PageRank link popularity scores.
NOT count the anchor text in determining what terms the page being linked to is relevant for.
That's the situation at the moment. Google is going to evaluate how the attribute works, and it could decide to make other changes down the line, it says.
Now let's look at the impact of each action:
1) Not following the link to the page it points at means that potentially, Google might not index the page at all. As said, the more links that point at a particular page, the more likely it is that Google (and generally the other major search engines) will include that page within its index.
The nofollow attribute DOES NOT mean that someone will prevent a page they do not actually control from being indexed, however. If Google finds even one ordinary link pointing at a page, it may then index that page.
In addition, people can submit their pages directly to Google (and most major search engines). So it's crucial to understand that just because someone might place nofollow in a link pointing at your site, this WILL NOT prevent your page from getting indexed.