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SEO: Using "Nofollow" for External Links & Preserving Page Rank


By hagrin - Posted on 05 January 2007

SEO Guide: Using "Nofollow" for External Links & Preserving Page Rank

Posted By: hagrin
Date: 20 December 2005

Overview:
Search Engine Optimization (SEO) remains the ultimate goal of the webmaster, blog publisher, e-commerce seller, AdSense user and pageview junkie. By tweaking and modifying your website's layout, design and content, a domain owner can increase his listing rank when terms are searched on the major search engines (for the purpose of these articles, the major search engines are Google, Yahoo! and MSN). One SEO hint/tip/issue that website owners should adhere to is preserving page rank through careful selection of external links. This article will define a lot of the terms used such as page rank, external links, etc., explain how the rel="nofollow" attribute works in preserving page rank, the possible drawbacks and an implementation plan.

What are External Links & How Does it Affect my Page Rank?
A major concern for website owners trying to optimize their sites deals with page rank within search engine result pages. Page rank is defined by Google as:

PageRank relies on the uniquely democratic nature of the web by using its vast link structure as an indicator of an individual page's value. In essence, Google interprets a link from page A to page B as a vote, by page A, for page B. But, Google looks at more than the sheer volume of votes, or links a page receives; it also analyzes the page that casts the vote. Votes cast by pages that are themselves "important" weigh more heavily and help to make other pages "important."

Important, high-quality sites receive a higher PageRank, which Google remembers each time it conducts a search. Of course, important pages mean nothing to you if they don't match your query. So, Google combines PageRank with sophisticated text-matching techniques to find pages that are both important and relevant to your search. Google goes far beyond the number of times a term appears on a page and examines all aspects of the page's content (and the content of the pages linking to it) to determine if it's a good match for your query.

If you thought that was a mouthful, you can read the explanation of page rank offered by Iprcom (this resource is for the math lovers only. Another good resource for explaining page rank can be found here at Web Workshop). So with Google's definition and a formula for calculating page rank, what does page rank have to do with how we post links to other websites on our site or blog? Web Workshop describes the potential harm that outbound links cause to our page rank as the following:

Outbound links are a drain on a site's total PageRank. They leak PageRank. To counter the drain, try to ensure that the links are reciprocated. Because of the PageRank of the pages at each end of an external link, and the number of links out from those pages, reciprocal links can gain or lose PageRank. You need to take care when choosing where to exchange links.

So, we see that we want to maximize our incoming links from other sites while limiting the amount of outbound links to otehr sites. This may prove difficult for some sites that report news since most of the content will come from outside sources. In addition, even original content writers use resources and it's generally good practice to list your references. Well, seems that we are between a rock and a hard place. However, in 2005, the major search engines adopted a new attribute for the anchor tag - rel=nofollow.

Using the "rel=nofollow" Attribute
What exactly does the rel=nofollow attribute do and how do we use it? Well, if you choose to make a link to another website and add the rel=nofollow attribute to the anchor tag, then search engines (when crawling your page) will not counts these links as an outbound link. They will act as functional text links to users, but no more than text to the search engine. Obviously, the benefit of this comes from being able to build highly informative web pages without enduring the page rank leakage from including external links. How do you actually use nofollow? Well, let's look at the example code below:

<a href="http://www.hagrin.com" rel="nofollow">Hagrin.com</a>

As you can see, it's very simple. Just make a link as you would normally do and then just add the rel="nofollow" attribute. It's really that easy.

Potential Drawbacks:
With most SEO tricks and tips, there are portential drawbacks for sure. Although no site directly talks about penalties directly associated to overuse of the nofollow tag, the blogging industry frown heavily upon using nofollow even in cases of trying to combat comment spamming. In addition, many people have come up with CSS snippets that allow them to browse a page and have nofollow links highlighted in a manner that makes it clealry visibile that nofollow is being used. The CSS used by some would look something like this:

a[rel~=”nofollow”] {
border: thin dashed firebrick ! important;
background-color: rgb(255, 200, 200) ! important;
}

This will alert readers to your use of nofollow and potentially cause "bad karma" for your site. Therefore, you may want to consider how heavily you use nofollow and for what sites you will use it for. Hopefully, with extremely directed usage and a little thought, you will be able to maximize your page rank by controlling the external links offf of your site.

Resources:

  1. Official Google Technology
  2. Iprcom Page Rank Explanation
  3. Web Workshop Page Rank Explanation
  4. Matt Cutts' Nofollow CSS

Version Control:

  1. Version 1.0 - 20 December 2005 - Original Article