The success of Google's search algorithm centers round using inbound links to a website to judge its relevance and importance relative to a keyword.
Over the years, SEO companies have come up with link building techniques to up their client's websites in Google's ranking. Google's original algorithm is being manipulated by all these techniques, and many high ranking sites are often irrelevant and unimportant. But Google keeps fighting back.
Such have been Google's improvements, that some declare that SEO is dead. Google has become skilled at detecting un-natural linking patterns; links to a website whose only purpose is to improve Google ranking. Many SEO experts are going back to fundamentals: What is a natural link ?
A Natural Link: The Referencing of Good Content by an Informative Author
Google's algorithm, as filed in Google's US Patent Application #20050071741 - Information Retrieval Based on Historical Data, is based on the Garfield's Scientific Citation Index, which is used to judge importance of research papers in the world of academic publishing.
Scientists write their results in research papers. Each research paper references all the other work that has contributed to its results. Important research papers that make a big breakthrough, give rise to more investigations, and are referenced widely. This citing and referencing is what the Google algorithm is looking for. Natural value-added links.
So, what does the natural linking look like:
1. Natural links are deeplinks. Links that point to specific material deep within the body of knowledge.
Deep linking is linking that points to a specific page or image within another website,
as opposed to linking to a website's main or home page. Deeplinking goes hand in hand with the long tail.
2. Natural linking is not reciprocal. Scientific papers are published sequentially in time. More recent papers reference older papers as they try and build the body of knowledge. Link exchanging, where websites exchange links, is not natural.
3. Natural links are built slowly over time. A seminal academic paper accumulates references, links, slowly over time. It is only well established highly regarded academic papers, like the discovery of DNA, that accumulate large number of references quickly.
4. Natural links make a point. Academics construct an argument around their references. So natural references are surrounded by relevant text and have specific anchor text, as each scientists tries to make his own point. The ratio of number of links to text has an upper limit, the density of links is relatively low, and the context surrounding the reference is relevant material.
5. Natural links come from everywhere. Scientists publish their research in many places. From important journals, like "Nature", to less important conference proceedings. So, natural links come from varied sources of relevant material.
Search Engine Optimisation is not dead, but it just got harder