by Richard Gilmore
Links are the fuel of SEO and just like gas they may have different octane rating called link value. Fuel your car with low-rate gas and it won't take you far. Same is true about links. You need to power your site with high quality link fuel if you want to make it to the top of search results and make it fast.
No two links are created equal. When building links it's important to be able to forecast the effect they will have on your rankings. The value of each link depends on a variety of factors that determine whether the link will give your site a huge jump in the rankings, help you climb a couple positions up or quite oppositely may result in a ranking loss.
That said let's see what factors contribute to link value and how you can evaluate the SEO efficiency of your current or prospective links.
Here are some of the most significant link value factors that make up the SEO value of a link.
These factors break down into 3 categories: the properties of the link itself (we shall call them link factors), the qualities of the web page where the link is placed (page factors) and the properties of the linking domain (domain factors).
Link Factors
1. Anchor/alt text
The anchor text or alt text in case of an image link has a huge effect on your rankings, particularly it determines for what search terms your site will be ranking higher. Having a good keyword relevant anchor text will help you get ranked for these search terms, however it's also need to vary your anchor texts to make sure your link profile looks natural.
2. Nofollow/dofollow
If the link has a nofollow attribute search engines don't count it when ranking sites. However there are speculations that nofollow links do pass some link juice. Anyway there's nothing bad about having nofollow links. In fact many SEOs believe that nofollowed links contribute to a natural looking link profile.
3. Link type (text or image)
Text links are considerably more valuable than image links, though the latter are also helpful.
4. Link age
Just like domains and web pages links tend to accumulate value over time, however poor quality links usually remain just that - aged poor quality links.
5. Total number of links on the page
The link value is distributed among all the links on the page therefore the fewer links on the page the more link juice each link carries.
6. Link location on page
The links placed higher upon the page get more value than those below. The value of the footer links and sitewides is said to have been devalued over time, though they still can give you a nice push up in the rankings. The best quality links are in-content links with an anchor text that is relevant both to the content on the page and to the page it links to.
7. Reciprocal/one-way
One way links usually pass more link value than their reciprocated counterparts. Despite all the talk around how reciprocal links are dead, two way links are still valuable, given that they originate from relevant sources. Reciprocal links can be and often are a natural phenomenon. Sites from one niche tend to link to each other all the time, so there's nothing wrong about having two way links. More over many experts believe that having different types of links makes up for a more natural and more effective link profile.
Page factors
1. Excluded from indexing (robots.txt)
If the page where your link sits is excluded from indexing, your link won't be indexed as well, so the search engines won't even know it's there.
2. Context
The textual context surrounding your link is just as important as the anchor text. If you get a link with 'web design company' in the anchor from a page about making an apple pie that link will be as effective as the one from a page about building a website.
3. Page authority (PR & link popularity)
We've heard it a hundred times and again. Toolbar PageRank (TBPR) does not equal the 'real' PageRank and should not be treated as such. We've heard it from experts, we've heard it from Google themselves that we shouldn't measure the authority of the site by the green bar on Google toolbar. Still since there's no way we can find out the actual PageRank, TBPR still remains the only indicator of that important (though not the only) ranking factor.
Alongside with PR it's important to take note of the quantity and quality of links pointing to the site, the number of indexed webpages, the cache dates (the more often pages are crawled and cached, the more important the website is for Google), mentions in social media, etc. All these factors contribute to the overall page authority.
4. Page Age
Google and other search engines tend to put more trust into the aged webpage, so a link on a older page tend to pass over more link juice. However you need to consider other factors that can magnify or degrade the effect of the page age. If the page has not gained trust and authority in the search engines, its age doesn't matter much.
With the release of Google Caffeine Google tends to put more emphasis on fresh content putting newly created pages from authority websites high up in the search results. So if you get a link from a new page on a trusted domain that may also add to the effect of the link on your rankings.
5. Relevance of outgoing links on the page
If your link sits on the page that also links to sites on gardening, PC gear, airplane designs and latest celebrity gossip you're not pulling much juice from it. On the other hand, if the page only links out to relevant sites in one niche the effect of those links is much higher.
6. Amount of textual content vs links on the page
The content-to-links ration on the page is an important link value factor. All-link directory type pages tend to pass on less value (unless they come from a highly authoritative site like DMOZ or Yahoo! Directory) than links on pages with a considerable amount on textual content on them.
7. User-generated vs editorial
If everyone and his dog can get a link from a page, there's not much value to those links. Search engines tend to put more trust into editorially created links rather than those that sit on user-generated pages.
8. Search rankings
If the page where your link sits ranks well for your target keyword (the one you use in the anchor text) or relative terms this makes your link more effective.
It's not quite a link value factor, rather an indicator of the page's overal authority, but it's an important thing to keep in mind when building links.
Domain Factors
Domain link value factors pretty much mirror those related to the linking page though there are some unique domain factors as well.
1. Domain authority (PR, link popularity, etc.)
Same as page authority only applied on the domain level.
2. Domain Age
Older domains tend to accumulate more trust and ranking power.
3. Domain relevance
Same as page relevance only applied to the domain level. It can be much harder to tell whether the domain is relevant or not because many websites tend to cover a variety of topics, so page relevance seems to be a more important factor.
4. TLD (.com, .org, .gov, etc.)
It's arguable that links from .gov and .edu sites are more valuable than links from .coms or .nets. The TLD doesn't play a big role by itself, it's just that .gov and .edu sites tend to accumulate quality links from other trusted sources which makes links from these sites more effective.
Bottomline:
These are some of the major factors that determine the SEO value of a link. Of course the more powerful your links are the better, but don't get obsessed with building only one type of links (e.g. only high PR one-way link). Having a natural link profile ensures better results in the long run.
This list is by no means exhaustive and unless Google discloses its ranking algo we won't be able to come up with a complete list of link value factors. If you have more factors to contribute, stop by and leave a comment.
P.S. Checking link value factors by hand is a hell lot of work to do, and is just plain impossible if you build links on a scale. This free backlink checker will help you quickly analyze large sets of backlinks and pick the best link sources.
