People have often claimed that a link within content on a page has more value than one form the sidebar or footer of a page. Whilst there is an argument that this is true because a link surrounded by content can be checked by a search engine robot for its relativity as it pertains to the content in which it is surrounded by there is another reason why this may be true.
VIPS or VIsion-based Page Segmentation is a technique used by search engines to determine the most relevant areas of a page. There are certain areas of a typical website that tend to be generic across a website and therefore offer no particular relevance to any specific page of a website.
As you will have noticed most websites contain navigation at the top of a page with additional menus in either the left or right sidebar plus a footer section. What VIPS aims to do is identify these sections of a page in the semantic mark-up of a webpage in order to be able to apply a more accurate weighting for the content on the page. Below shows a example (source) of the different areas that can be defined when using a VIPS system.
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How Is VIPS Used by Search Engines?
The important thing however is how these blocks of content on a web page are valued once they have been defined. This is how the algorithm works to determine the relevant areas of a page, as you can see there is a granularity requirement which is an interesting feature of the algorithm.
Because not all website and web pages use the W3C standard for HTML and CSS mark-up it would be possible for the algorithm to incorrectly identify areas of the page or even be unable to segment the page effectively. So to stop manipulation of the weight of the links on a page either intentionally or unintentionally the algorithm must check the resulting page structure determined by the algorithm against an accepted degree of granularity.
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Link Relevance in The Future
The goal of the search engines is to index and display quality content; they are able to achieve this by lowering the quality and relevance of certain areas on a page. Looking forward I would expect search engines to try and make the use of links that are not beneficial to site content even less relevant.
One of the ways I see this happening would be by the segmentation of comments from a page. A lot of people use comments as a way getting links back to their site however it can be assumed that a full page article with links to a relevant source will have more weight than a comment on that article containing a link. In fact it is likely some sort of segmentation to lower the value of links from comments from web pages is already in use.
With the massive popularity of content management systems such as WordPress, Drupal and Joomla it is much easier for search engines to determine the blocks of content on a page due to the consistent semantic mark-up these platforms utilise and thus give less weight to the comments placed on these pages.
How to Get the Highest Quality Links
In order to get the most value for your links you will want to have a link coming from the content area of a page which is preferably on topic as well. The main and most effective technique for doing this that I have currently seen is by the use of guest blogging. Using guest blogging as your method to create back links for your website allows you to get links in the content area of a high status page.
This is not only beneficial to you but also the search engines who have found a way to entice people to create quality content in order to rank well and ultimately comply with the rules that are imposed upon websites with algorithms that incorporate the use of VIPS.