You've put in months or even years of work on your web site. You've researched keywords and targeted your content meticulously. Your code is clean and your pages load quickly. And still, the search engines still don't rank your pages highly enough. What to do? The obvious answer is to get more links. But if you think building a network of sites just to increase your link profile is the solution, beware. This is called link farming, and it's a sure fire way to send all your hard work down the drain.
Since the early days of search engines, webmasters have realized the importance of a robust portfolio of inbound links. But natural link building is time consuming and effort intensive. In those early days, search engines were not as sophisticated as today, and webmasters could simply create a network of sites solely intended to pass link juice to one main site. This strategy may have worked back then, but today it can be a poison pill for your search engine rankings.
Today, many unethical SEO practitioners still push the practice of link farming on their unsuspecting clients, despite knowing that it breaks search engine rules and provides only short-term benefit to their clients at best. The basic theory is this: search engines cannot tell the difference between a well-intentioned inbound link to your site, and a link from a fly-by-night web site which was created simply to give you that link. While that may have been true at one time, the search engines have a great deal invested in defeating webmasters who try to game the system, and their algorithms have become fully capable of spotting a link farm.
For one thing, search engines have access to all the information they need to determine whether two sites are related. Web sites leave an ownership footprint, including such factors as the server's IP address and WHOIS (ownership) information. If you own 50 sites on the same server which all linked together, the search engines can tell. At best, they will discount the links between these sites, and at worst, the sites can be de-indexed altogether.
Even if you take extraordinary measures to mask your link farming, your link profile can give you away. Let's say you've gone so far as to host all of your web sites on completely different servers in different locations, an expensive and time-consuming process. Let's say you've also used various services to make your ownership of your sites anonymous, used different domain registries and made your sites look as if they were owned by 50 different people. Even then, you risk being discovered as a link farm due to your telltale link profile.
In fact, link farms are often maintained by a variety of owners, and search engines are smart enough to spot them. How? Google patent documents provide some clues. These documents contain diagrams of some of the unnatural linking patterns that indicate link farms, and they are not always straightforward. For example, site A may link to site B, which links to site C and so on. In a link farm however, the sites eventually form some type of a circle, perhaps with site Z linking back to site A. Search engines have more than enough computing power to establish that all of the sites are ultimately connected.
You may wonder how this is different from a normal group of web pages, which often link back and forth. Search engines also take into account the link profile of each and every element of the chain of sites. If a series of sites link together or all link to one site, and they do not also link in and out with other quality sites, they create what SEO experts call a “bad neighborhood.” Linking to or from a bad neighborhood tells the search engines that your site is suspect. Link farms are the ultimate bad neighborhood. When a search engine sees a number of links to your site from such a neighborhood, they can decide that your site is not worthy of a high ranking.
Some links from bad neighborhoods are to be expected. After all, you don't have control over who links to your site, and search engines try not to penalize you for natural behavior. There is little doubt that major sites like Amazon and Ebay have many inbound links from spam sites, link farms and other bad neighborhoods. The key is that their overall link profiles look natural. The vast majority of their inbound links are from reputable sites which themselves have solid link profiles. Therefore they are not effected by links of lesser quality. It's when a site is young, with a small link profile, that link farms can hurt. Given the time, effort and risk involved in creating a link farm, it's just not worth it.