Since Google introduced its PR (page rank) based search engine, the way it evaluates links changed substantially. Whilst at first “link popularity” (amount of links pointing to a site) was key, today a number of different factors decide how much weight a link carries. The sheer number of links is secondary. Its quality over quantity.

 In the following I will list the 10 most important factors.

 1. Relevance

 This is probably the most important one. An inbound link from a site that is about the same topic as yours carries the most weight. The reason for that is just logical: A site that links to additional content about the same topic is providing the user with an added value.

 Lets say for example, you optimized a site about “American politics”. In this case the site: www.whitehouse.org would carry more weight then I.e: www.amazon.com , simply because its more relevant.

 2. Link text

 The link text tells the user what the site linked to, is all about in a few words. Often this is just one or two words. Search engines value the link text very high, because it is a third party recommendation to what the site is all about. Your site will most of the times get indexed, under the words you use in your link text , also referred to as “anchor text”.

The biggest mistake webmasters make is using “click here” or “go to website” as anchor text. This accounts for inbound links, as well as for your internal links. Instead your keywords should be used as anchor text. Make sure you are not using always the same keywords – that would not look natural hence is not credible and might get your site “flagged” or “sandbox-ed”.

 Search Engines also read and take into account the text surrounding a link. It pays to have a good description under a link.

 3. Links from trusted sites

 These are sites that are authorities on a topic and are around for some time. A link from this kind of site carries a lot of weight, but these links are difficult to obtain. If you can not get a link from a “trusted site” then try getting one from the sites the trusted site already links to. The closer you are linked to a trusted site the better for your “link profile”.

 An example: If you optimize for the term : “virtual worlds” the site: www.secondlife.com carries more weight then most other sites about virtual worlds. It is a topic authority and a trusted site.

SEOs do spend a considerable amount searching the web to find trusted sites or sites a trusted site has linked to.

 4. Diversity

 This is what determines your link profile. The more you have links from a variety of sources the more credible is your link profile.

 This includes links from a diversity of IP addresses, domains, high and low page rank, types of site and topics. If all of your inbound links do come from the same or similar  IP’s, they carry less weight than if they were all from different sites/IP’s. It is also important to get links from different types of sites: communities, blogs, directories, wiki’s and so on.

 5. Age

 The value of a link increases over time. The longer a site links to you, the more this link will impact your rankings. This is especially the case with sites, that do often change their content but do not remove the link to your site. It is therefore  paramount to check your links  on a regular basis and give your linking partners a good reason to keep that link.

 6. Position of the link

 It does make a difference, where the link is on a given page. The highest value do have links, which are within the content of the page. For example in an article. The lowest value carry links in the footer of a page.

 7. Amount of outbound links

 You share the value a link from a given page can carry , with all other links on that page. Lets say, for example,  the value of a certain link would be 10 points . But there are 9 other links on that same page. That means the link to your site is valued at 1 point only (actually a little bit less as the sending site holds some of the value back).

 Google also takes into account the amount of outgoing links of the entire domain in relation to the actual content of the site. Therefore sites that have thousands of outbound links but not much content, or pages with hundreds of outbound links are not a good source for links,unless they carry a lot of weight for other reasons ( topic authorities).

 A page/site that ONLY contains hundreds of links is worthless at its best and dangerous for your site at its worst. Most of them are what we call “link farms”.They have no value for the user and are created for the sole purpose of obtaining link popularity.

 8. PR (page rank)

 The page rank of your site as such does not determine how well you rank and does not impact your rankings as such directly. Page rank shows you, how Google evaluates a given page, based on the above factors. That means that a link from a site/page with a high page rank carries more weight then a link  from a page with low or no page rank at all.

 9. The nofollow attribute

 The nofollow attribute is an HTML element, that is used to indicate search engines, that the creator of the site does not vouch for the site he is linking to. Those links are pretty much worthless from an SEO perspective.

 However often sites that could refer a lot of visitors to you use the nofollow attribute to avoid link spamming.

 Here two examples: www.wikipedia.org or  www.xing.com.

The later being one of my biggest and most important referrers.

 10. Reciprocation of a link

 If you link back to the site/page that links to you, both links loose a considerable amount of their weight. In fact, the remaining weight is not much higher then the weight of an internal link. Reciprocal links are only worth doing,  if the the two site do offer the user a genuine value, meaning the two sites need to be very relevant to each other. For the purpose of link exchange it is a much better strategy to set up a second website on the same topic.

 Then you have site B (Your on topic link exchange site/blog)  linking to site C ( the site you want to exchange links with) and C linking to A (your main commercial site). Your site B may also link to A. Make sure that you have good and unique content on both sites and host them on different IP addresses.

 Resume

 As you can see, building a good link profile is not as easy as it might look like. It requires time, knowledge of how to evaluate sites and experience. This is why companies hire SEO professionals instead of doing it themselves.

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