The following is an excerpt (with some recent modifications and editorial comments) from our book, WordPress Search Engine Optimization (now in second edition!). You can buy the book at Amazon.
Authority Links: What They Are and Why You Want Them
There is a measure of power that some links possess that is independent of PageRank and it is the principle of authority links. Authority links are links from websites that have established a substantial degree of trust and authority with search engines as a result of their age, quality, and size. Authority is a somewhat subjective concept. Unlike PageRank, neither Google nor the other search engines offer any public reference or guidelines as to what constitutes an authority site or authority link. Authority sites are going to be the market leading sites, sites representing established government and educational institutions, large corporations, or leading websites. Authority links can bring tremendous ranking power to a website if one is lucky enough to obtain one or more.
Authority links are the golden eggs of link building. They tend to be extremely difficult links to get, and for that reason most webmasters rarely get them. The best approach to authority links is to be vigilant for opportunities to obtain them, but it is most likely fruitless to waste time in seeking them out.
Our discussion of PageRank and authority links leads naturally to the notion of the relative power of inbound links. No two links are the same in terms of power. The degree of authority of a site, the PageRank of the page upon which the link appears, and the number of outbound links on the page where your link appears will all effect the relative value of the links you obtain. That said, almost all links are worthwhile, even lower value links. With what we’ve learned in the previous few pages, you will have a strong sense of how to evaluate link opportunities and to evaluate the relative strength of links.
Sometimes, you’ll be forced to settle for lower value links but in higher volumes, as is the case with link directories. But never fall into the trap of thinking that the only links worth getting are high-authority, high-PageRank links. All links are good for your rankings (except links from link farms and content farms, from which you should never seek out links).
Link Anchor Text
A vital concept in link building is link anchor text. Link anchor text is the word or words that constitute the visible text of the link itself, the “blue underlined text” as it is often called. The anchor text of a link is a powerful ranking factor; anchor text serves as a signpost to Google as to the content and subject of the destination page.
How Anchor Text Appears in HTML Code
The anchor text of a link is coded by placing the desired text between the open and closing markup of the hyperlink:
<a href="https://www.tastyplacement.com/">This Is Anchor Text</a>
Controlling the link anchor text of inbound links is vital whenever possible. The problem is that you can’t always control the anchor text of inbound links. And unfortunately, the higher quality the link, the more restricted you’ll be in choosing anchor text. A perfect example is the Yahoo Directory. A link in the Yahoo Directory is a great link to get, but Yahoo dictates that the anchor text you select be the name of your website or the name of your business. Yahoo does not allow you to stuff keywords into the anchor text. Here lies another good reason to choose a keyword-rich domain name for your website and business. When your business name is carefully crafted to comprise keywords, like “Austin Air Conditioning,” then you can employ those high-volume keywords more easily in your link building efforts.
To continue an example from an earlier chapter, if you have identified the phrases “Jacksonville air conditioning,” “Jacksonville air conditioning contractors,” “Jacksonville air conditioning companies,” and “Jacksonville air conditioning repair,” as the keywords around which a specific page is built, then your anchor text selection is nearly complete. You can use the same keywords as your desired anchor text.
When you can control the anchor text, you should craft the anchor text of links based upon the keywords you have designated for each destination page. With this device used in connection with sound on-page optimization, tremendous ranking power comes into focus. Remember that Google and the other search engines have a primary goal of returning quality search results to their visitors. When anchor text accords with the on-page elements of a web page, that gives search engines confidence as to the subject of that page. And, when a search engine is confident about subject matter, it rewards the page with high rankings.
But be careful with anchor text when gaining links in high numbers. It is unwise to secure hundreds of links all with picture-perfect anchor text; this manner of link building does not appear natural to search engines. There is a risk of over-optimization when your link anchor text is too perfect. Generally, you never want more than 70% of your anchor text for a particular page to be solely based upon a small family of perfect keywords. Thus, there is a hidden benefit to garnering links for which you can’t control the anchor text because these links dilute your principal keywords to some extent.
If your anchor text isn’t varied naturally, then you should intentionally vary the anchor text. Clever SEO professionals sometimes go as far as to obtain noise links. A noise link is a link with common generic terms used as the anchor text like “click here,” or “website.”
Not all hyperlinks have anchor text. Images can be hyperlinks, but do not use anchor text. In this case, search engines register the link, but have no anchor text upon which to determine the subject matter of the link. Links in image maps and flash files suffer from the same limitation. For this reason, such links are less desirable.