How do search engines evaluate links?
Since the late 1990s search engines have treated links as votes for popularity and importance in the ongoing democratic opinion poll of the web. The engines themselves have refined the use of link data to a fine art, and use complex algorithms to perform nuanced evaluations of sites and pages based on this information.
Link Signals used by Search Engines
How do search engines assign value to links? To answer this, we need to explore the individual elements of a link, and look at how the search engines assess these elements.
We don’t fully understand the proprietary metrics that search engines use, but through analysis of patent applications, years of experience, and hands-on testing, we can draw some intelligent assumptions that hold up in the real world.
Globally popular websites are great to have links with
The more popular and important a site is, the more links from that site matter. A site like Wikipedia has thousands of diverse sites linking to it, which means it’s probably a popular and important site. To earn trust and authority with the engines, you’ll need the help of other link partners. The more popular, the better.
Local Topic specific popularity
The concept of ‘local’ popularity, suggests that links from sites within a topic-specific community matter more than links from general or off-topic sites. For example, if your website sells cat baskets, a link from the Society of Cat Breeders matters much more than one from a site about deep sea diving.
What’s so important about Anchor Text
One of the strongest signals the engines use in rankings is anchor text. If dozens of links point to a page with the right keywords, that page has a very good probability of ranking well for the targeted phrase in that anchor text. You can see examples of this in action with searches like ‘Click Here’ where many results rank solely due to the anchor text of inbound links.