External Factors for Search Ranking Position

Reciprocal Links
A long time ago, webmasters used to trade links strategically to achieve radical improvements in rankings. This created an artificial number of self-serving votes. Over time, search engines became wiser and they devalued such reciprocal links. In response, search engine marketers created link-exchanging schemes with multiple parties to avoid detection. Modern search engines can detect such simple subterfuge as well. That is not to say that reciprocal linking is bad, but it should be balanced by several one-way links as well. The combination of the two models something more natural-looking and will result in higher ranking.

Number of Links on a Page
A link on a page with few outbound links is generally worth more than a link on a page with many outbound links. This concept is also implied by the formula for Google’s PageRank.

Semantic Relationship among Links on a Page
A search engine may assume that a page with many links to pages that are not semantically related is a links page, or some sort of page designed to manipulate rankings or trade links. It is also believed that even naming a page with the word “links” in it, such as links.php, may actually devalue links contained within that particular page. So do name your URL wisely such as resources.

IP Addresses of Cross-Linked Sites
It is sometimes useful to think of an IP address as you do a phone number. For this example’s sake, format a hypothetical phone number, (123) 555-1212, differently—as if it were an IP:
IP addresses located in the same C class — that is, addresses that match for the first three
octets (xxx.xxx.xxx.*) — are very likely to be nearby, perhaps even on the same server.
When sites are interlinked with many links that come from such similar IP addresses, they will be regarded suspiciously, and those links may be devalued. For example, a link from domainA on 100.100.1.1 to domainB on 100.100.1.2 is a link between two such sites. Done excessively, this can be an indicator for artificial link schemes meant to manipulate the rankings of those web sites.

TLD of Domain Name for a Link
It is widely believed that .edu and .gov domain names are less susceptible to manipulation and therefore weighed more heavily. This is disputed by some search engine marketers as the actual factor, and they assert that the same effect may be as a result of the age (most schools and governmental agencies have had sites for a while), and amount of links that they’ve acquired over time. It is mostly irrelevant, however, what the underlying reason is. Getting a link from a site that fits this sort of profile is very desirable — and most .edu and .gov domains do.

Link Location
Links prominently presented in content near the center of the page may be regarded by the search engines as more important. Links embedded in content presented near the bottom of a page are usually less important; and external links at the bottom of a page to semantically unrelated sites may, at worst, be a criterion for spam-detection. Presentation location is different than physical location. The physical location within the document was historically important, but is less of a factor more recently. Ideally, the primary content of a page should be early in the HTML source of a web page, as well as prominently displayed in the center region of a web page. More on this topic is discussed in Chapter 6, "SE-Friendly HTML and JavaScript."