Isn’t this the main purpose of Google’s algorithm? They seem to be pretty good at it. Your website topic is not a part of Google’s algorithm, they achieve high relevance in SERPs by using a more granular approach. Simply put, they analyze and index individual documents, not websites.
If you’d like a demonstration of how well they can do this, and how quickly they can do it, simply enter the URL, where your article about an iPhone App is placed on your blog about auto insurance, into the AdWords Keyword Tool. This nifty tool uses the core “relevancy” algorithm to instantly analyse your page, finds most of the important keywords that are “relevant” to that individual page and even automatically sorts them by relevance. That last part is very significant, it demonstrates their ability to determine the degree of relevancy for each individual word.
That portion of the algorithm calculates and scores the on-page relevancy factors. The calculation for relevancy of inbound links is performed in a similar fashion, allowing for the different contextual application of proximity and prominence (core principals of Google’s algorithm). This slightly different approach applies more weight to the anchortext followed closely by the words near the anchor that links to the indexed page, since those elements are closer in proximity and promenance, relative to the indexed page.
Google’s algorithm is not only able to tell that your article is relevant, (absolute value), it is able to determine the degree of relevance (relative value). Google’s superior application of the principals of prominence and proximity are part of their core competency. This effective approach produces a relatively high degree of relevancy in their query results and has led to their dominant position in the search engine industry..
I think some folks may be too quick to dismiss the importance that relevance plays in earning high SERP rankings. Backlinks without relevance may pass PR value, but PR alone wont get you ranked. That value must be channeled through a relevant link before you will get any increase in the relevancy score used to sort your position on the SERP.
I believe if we choose to look at relevance from a webmaster’s perspective we may fail to see how a search engine determines relevancy. For us to be effective at SEO it may be helpful to understand relevancy from the perspective of the search engines. Does it matter what you or I call relevant, or irrelevant? Or is it more important to understand what Google considers to be relevant?
Google, nor any other major search engine, uses website topics to determine relevance. The primary reason search engines exist is because a more granular approach was needed to go beyond limitations of a website directory organized by website topic.
Many of the earliest search engines used meta tags, but these were not used universally and were frequently abused. Google revolutionized the industry by developing an engine that read the visible content of a web page and analyzed the relevant keywords contained within the content. This ability combined with the ability to determine relevant inbound links, weighted by popularity (PageRank), to form a relevancy score that is used to sort the listings of the SERP. This same core concept is still at the root of Google’s algorithm today.