What is Latent Semantic Indexing?
Latent Semantic Indexing, or LSI, is a way for search engines to view and rank web pages in a natural and visitor orientated, manner
- LSI algorithms analyze pages not only for keywords, but also for synonyms and other related words which might be expected to be present
- For example, a web page about houses, when analyzed with LSI, should logically also contain such related words as “rooms”, "garden", "kitchen", "bathrooms", “garage” and "decoration"
- We do not know the exact mathematical formula used for LSI by the various search engines, nor do we know how important LSI has become in the overall search engine ranking algorithms
- We do, however, know that latent semantic indexing's real function is to determine if the content of a site is of value to the visitor or not.
HISTORY OF LSI
Google earns billions of dollars from adsense and adwords, which are essentially advertisements.
Initially, Google Adsense matched keywords on the pages to keywords in the ads and a website owner earned money for every click he received from an ad shown on his site
- Millions of pages were being generated simply to contain relevant long-tailed keyword phrases to capture traffic from Google and the resulting profitable clicks on the ads
- Content on the machine-generated pages was virtually non-existent and it was a frustrating experience for the person doing a search to only find spam
- Google's reputation, and long-term financial status was at stake
- The problem for Google at this time was that they could not differentiate between these generated pages and the sites which actually contained valuable content
- In 2003 Google purchased a company called Applied Semantics whose software technology was used to extract and organize information from websites in a manner similar to the way of a person
- The purpose of purchasing LSI technology was to help Google match advertisers of Adsense ads with the appropriate web pages where the ads would be shown
CHANGES BROUGHT ABOUT BY LSI
Themed Sites and Searches
One of the ways LSI has changed the way Google looks at sites is a shift from "keyword" to "themes"
- Today, and in the foreseeable future, it will be more advantageous to build sites around a number of related words and synonyms instead of around a single keyword
- Secondary keywords can be defined in a number of ways but some refer to related keywords and synonyms as secondary keywords
- People are not looking for pages that contain specific keywords, they are looking for sites built around a theme
Anchor Text
In the past, SEO techniques have been to focus on a single keyword, or keyword phrase, for both external and internal links
- The thinking was that if one particular keyword was bringing in the most traffic, it should be the one used throughout the site
- However, with the introduction of LSI, sites that previously were ranked high because of extensive inbound links based on a single keyword have now found their rankings have fallen
- LSI looks for a more normal approach to linking
- Instead of one keyword or keyword phrase being used as anchor text, a variety of anchor text is favoured
Current SEO strategies in light of LSI
Although we don’t know all the ramifications of LSI at this time it is nonetheless important to apply what knowledge we do have to achieve and maintain our desired rankings with Google
The following short list of tactics may help you get started:
- Develop themed pages on a broad scale rather than concentrating on one keyword
- Strive for more naturally worded and written pages
- Consider your keywords and try to include synonyms, related words, and plurals throughout your pages
- Do not seek reciprocal links
- One way links are far more valuable
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David Viniker, the author and webmaster of SEO4us.com, believes that quality of content is a prerequisite to success. He is a clinician (consultant obstetrician and gynaecologist - ObGyn at Whipps Cross University Hospital, London - borders of London and Essex). He has research and teaching interests. His website www.2womenshealth.com receives 1.5 million visitors annually and is the most popular personal women's health website on the Internet. He has applied his clinical skills to researching SEO techniques.
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