What is Link
A link (hyperlink) is simply a unidirectional pointer from the source page that contains the link to some destination, generally another page. Within a web page, links fall into five different categories: internal links, inbound links, outbound links, dangling links and dangerous links.
Each type of link: internal; inbound; outbound; dangling and dangerous should be strategically considered when designing, optimizing or maintaining an Internet web site.
Internal Links
The structure of a site’s internal links should be designed with search engine rank in mind. One should cluster pages within general themes. Key pages should be the recipient of links from all the various theme pages. I would also recommend having any ‘links’ page (e.g. a resource page) possessing a relatively few number of internal links directed towards it (this will be further explained in the discussion of outbound links).
Inbound Links
One of the most important aspects of high rankings and maintaining high rankings is the number of inbound links coming into your site, what is referred to as ‘link popularity’. The nature to this ‘popularity’ is not so simple as just the total number of sites that link back to your site.
There is also a qualitative characteristic to the ‘vote’. A page that links to a site that has a higher search engine ranking will contribute more ‘points’ to the ranking score then a page with a lower score.
Page ‘x’ linking to page ‘y’: the amount of importance conferred on page ‘y’ is proportional to the importance of page ‘x’ and inversely proportional to the number of pages ‘x’ points to. This is further explained in the ‘Google Elaboration’.
I do not want to over simplify the search engine spider’s algorithms, there is more involved in the analysis. For instance, the more ‘theme related’ sites that reference your site (with a link) the better the search engine ranking score. Theme, as defined by the content of your site (e.g. a computer software site linking to a computer software site is more valuable then a dog food site referencing a computer software site).
In addition, some links from certain pages carry no weight in ranking the referenced page. It is also possible for your ranking score to be penalized for having a link from a certain ‘flagged’ site, dangerous links (e.g. link farms).
Note: No inbound link can cause rank penalty to the targeted page. This makes total sense, in that one does not have control over the external pages that link to their site.
Outbound Links
All the links within a particular site that are directed away from that site have a negative affect on the search engine ranking score. This simply means that one needs to be very discriminating concerning outbound links. Discriminating web site ‘theme’ relatedness and site quality should be used to justify all outbound links.
Dangling Links
Dead end pages have a minimal affect on the overall search engine ranking score of a web site. This being said, one is loosing valuable opportunity by designing pages with dangling links. Therefore, every page within a web site would have at least one link to another page within that site.
Dangerous Links
Be very discriminating concerning outbound links, requests for inbound links and, most importantly, avoid any site with link farm characteristics. Link farms were setup to exploit the quantitative nature of ranking link popularity. They are not ‘theme’ related, rather their sole purpose was to develop mass ‘group’ linking to and from all of those who join the ’scheme’. These are now identified as a spamming technique, which will result in rank penalty or index removal. Avoid all link farms or any sites that even closely relates to them! Make sure none of the outbound links are dead links. Requesting inbound links from sites with good search engine ranking scores and focus on those sites with similar themes to the requesting web site.