So now that we’ve mentioned a few of the things you shouldn’t do, what are some search-engine-approved ways of driving traffic to your site? We’ll focus on Google, since they have the majority of the search market in western countries, but most of what we’ll cover applies to other search engines as well. Today we’ll talk about links and their effect on how Google views your website.
Everyone knows that incoming links are key, but what people don’t always realize is that the quality of those links are also important. Let’s take a quick look at the Google pagerank algorithm.
Every web page indexed by Google has an ever-changing rank between 0 and 10 that indicates how important, useful, and trustworthy it is; of the top 100 US sites according to Alexa, the average pagerank is about 7.5, and with the exception of the adult sites, all have PR at least 6; on the entire internet, there are fewer than two dozen sites that have a PR of 10. (By the site’s PR, we mean the PR of the home page; the PR10 sites generally have multiple pages with that rank). Pagerank uses a logarithmic scale, so as the value decreases, the number of websites with that value increases exponentially. Note that the integer pagerank is only an approximation and can change whenever Google does a PR update, which generally happens at least once a quarter.
Google considers each link from a webpage (except those with the nofollow attribute) to be a “vote” for its destination; the total PR of the page is divided by the number of dofollow links. For example, if a PR6 page has 30 dofollow links, that page contributes a 0.2 “vote’ to each page it links to.
People often try to abuse this system by buying hundreds or thousands of links, a practice frowned upon by Google; their official policy is that sponsored links should use the nofollow attribute. “Organic” links, however, can be very valuable. Let’s look at what does and doesn’t work.
Obviously, links from PR0 sites, particularly those that have a lot of outgoing links, aren’t worth much; ideally you want to have links from higher PR (4 or above) sites that don’t have many other links on the same page. Additionally, links are worth more if they come from a related site; if your site is about X and you get a link from a highly-rated site that is also about X, that link is worth more because Google considers the other site to be an authority on the subject. This can be a problem for ecommerce sites because related sites are likely to be your competitors and their owners won’t be interested in helping to increase your pagerank!
One thing Google watches for is the speed at which links are acquired; a site that goes from 8 incoming links to 20,000 incoming links overnight probably is paying for those links, so they’ll be discounted. Again, Google wants to see “organic” links – those that come about naturally because your site is useful to users of the referring site – and tries to reward them. Google also looks at the “neighborhood” your links are coming from; links from spammy sites tend to be discounted.
Another thing to watch for is the anchor text used for your link; a link of the form <a href=”yoursite”>relevant text</a> is worth a lot more than one that looks like <a href=”yoursite”>click here</a> (although Google does have algorithms in place to try to catch Googlebombs). Of course, if every incoming link to your site uses the same anchor text, that’s another sign Google can use to catch paid links; it’s also a wasted opportunity since you want to rank highly for multiple ways to phrase the same thing. Notice that webpages can even rank highly for terms that don’t appear on them (as in the George Bush / miserable failure Googlebomb) if enough links use that phrase; for example, searching Google for the phrase “click here” will bring up the page to download Adobe Reader, due to the many, many sites that tell their users to “click here” to download it.
More recently, Google also started looking at a site’s outgoing links; a site that mostly links to trustworthy sites such as wikipedia is likely to be regarded more highly than one that links to spammy sites. In other words, Google judges you by the company you keep!
Tomorrow: how to code your webpages to make Google happy.