One of the most difficult skills for a doing SEO of a website is to estimate the relative value of a link on a web page (page and location on the latter). The subject is complex because it is impossible to define an exact value without knowing the exact algorithm of Google, which of course is kept secret.
Is this a reason not to try to estimate? No, although it remains imprecise exercise, a good SEO person, thereby you the website owner, should be able to compare different sources of links and identify the most important. It must analyze several factors to be able to estimate effective links.

Link anchor
The anchor of the link (link text) has a high importance. It greatly helps your site to position on a particular query. A good link must use an anchor with a keyword relevant to your site.
Authority of the domain name
The number and quality of links pointing to the area from which the influence link quality. A link from an authoritative source on a particular topic can help you get a good position thanks to him alone for it.
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Contract Value
All sectors of the web have different values. Some areas are much more profitable than others, which explains the huge difference in income that can be drawn from a humor site versus a site of insurance for example. To get a link to a site of authority in the field of insurance worth so much more than an equivalent relationship with an anchor at a site equivalent authority of sport. Some areas have minimal source of available links (all sites are direct competitors) for example is often the case in the field of automotive. A link to a site independent of a sector that has little area thus has more value to its scarcity. Understand that some sectors is significantly of higher value (100 times) than other sectors, which explains the difficulty to position themselves in certain areas.
Authority of the page and internal links
The quality of the page or the link is located is also of great importance. A page with many incoming links and interesting content will provide a quality link on a specific topic. Consider, for example a page of a blog tutorial on receiving links from multiple sources on the Internet.
Age of the site / domain
We wrote with this subheading in some article ago, so now just touching it.
Although the age of the site itself is not a crucial factor for a good link, old sites are normally more content indexed, many links and a certain authority, so a link to an old site is normally better than a link from a site recently. Such links can greatly help a website to get the authority. It is important to understand that a site must be older still be a minimum standard to provide a benefit.
Number of outbound links on the page
The more outgoing links on a page, the less the amount of “linkjuice” link gone through is important. So, a partner link on a page with dozens of outbound links (and usually few external links is inbound) is much less powerful than a page with few outbound links. The ratio of incoming links / outbound links is important.
Total number of links
As the number of outgoing links, the total number of links in importance. The general idea is that a page with over 100 links no longer gives “linkjuice” links after the hundredth since the spiders stop indexing from there. Even if the number is speculative, it is a good idea not to put too many links on one page (including sitemap ; this varies case to case) and try to get links on pages that do not have too many links.
Location
Google judge the quality of links according to their locations on the page. Normally, a link at the bottom of page is less powerful than a contextual link. It is therefore important to place its bonds in an example sentence with content that supports the link anchor.
Age of the link
Another important point when one wants to assess the value of a link is its age. A recent link seems to weigh less in the algorithm a link present for several months. It is therefore important to maintain ties over a long period of time. This makes sense because it gives less weight to the link spam will be moderated and therefore have a shorter lifespan.
Link Type
A text link normally brings more weight than a link with image alt tag containing the keyword. We must also avoid putting a link on an image that has the size of a standard banner. For example, a standard banner is 468 × 60 pixels, which is easily detectable by bots, and possibly analyzed by search engines.
Text around the link
The text around the link has an influence on the value of the backlink. This is one of the things documented in the original patent from Google. It still remains an “Educated Guess” but it’s much more likely than not.
Reciprocity
A reciprocal link (a link exchange between two pages, for example) is less powerful than a one-way link. Have multiple reciprocal links is not a problem as long as the portfolio of bonds of a site does not consist only of such links. So it’s not bad either, but it should not be central to your strategy of acquiring links.
Target link
Have all its links to its homepage is not the best strategy of acquiring links. We must get a lot of links to its internal pages to better distribute the “link juice” between the pages of the site and promote the most important pages.
Robots.txt
A link from a page that is blocked by robots.txt site has no value. Since bots can not read the page, they will not read the link. It’s simple right?
Links on one penalized page
The links on a page that has been penalized has no value. It is therefore useless to try to get them. We are not saying that buying links does nothing, we are saying that sites that were caught do not spend any more linkjuice.

Oh my goodness! Amazing article dude! Thanks, However I
am experiencing problems with your RSS. I don’t know the reason why I am unable to join it. Is there anybody else getting the same RSS problems? Anyone that knows the solution can you kindly respond? Thanks!!
Yeap, there are some issues with Mac Safari with higher resolution. I myself also feel them. They will be fixed soon.