Search engine optimisation (SEO) is the science of making the most of a website in terms of attracting new visitors and potential clients.
SEO can be divided into on-page optimisation and off-page optimisation. On page optimisation relates to content within the website. Off-page optimisation involves increasing the total value of backlinks to the website. There is a recent vogue in the SEO world to refer to backlinks as “link juice.” Most experts in the field are agreed that off-page factors are more important than on-page optimisation in terms of top positioning on search engine results pages. If a website does not feature in the top 10 positions for a keyword it will receive few new visitors.
In a previous article (May 2010) it was demonstrated that PageRank is the most important factor in search engine positioning. Google treats home pages and internal pages differently. Google is interested in the PageRank of the home page PageRank of internal pages. Home pages competing for a keyword receive a boost to their PageRank score.
The relationship between PageRank and the number of backlinks has been analysed for 500 home pages. These were obtained on Google for several different countries for short- and long-tail keywords. The number of links were all determined from AllTheWeb.
PageRank (PR) Sample Number (N) Average Number of Backlinks (AB) Range (R)
PR1 (N) 64 (AB) 77 (R) 4-524
PR2 (N) 73 (AB) 166 (R) 2-2490
PR3 (N) 90 (AB) 615 (R) 13-5940
PR4 (N) 62 (AB) 2,458 (R) 23-10300
PR5 (N) 52 (AB) 69,311 (R) 48-503000
PR6 (N) 57 (AB) 253,237 (R) 88-5750000
PR7 (N) 57 (AB) 612,450 (R) 852-7280000
PR8 (N 37 (AB) 9,374,989 (R) 11800-173431000
PR9 (N) 11 (AB) 10,708,000 (R) 130000-32000000
It is no surprise that as a rule, higher PageRank is associated with a greater number of backlinks
This data reveals two interesting facts.
a. There is a large variation in the range of backlinks for each PageRank.
b. The range of number of backlinks for different PageRanks overlap.
To explain these findings we need to understand that the value of each link depends on:
1 The PageRank of the linking page. All else being equal, a link from a page with PageRank 6 will have twice the value of a link from a page with PageRank 3.
2 The greater the number of links on the linking page, the less the value of each link. One program calculates the value of each link by dividing the PageRank of the linking page by the total number of links on it. A link from a page of PageRank 1 with just one link would have a link value of ‘1’ but a link from a page with PageRank 5 with 10 links on it would have a value of 0.5. Links from pages with zero PageRank carry no link value. This would explain how some pages with 88 links can have a PageRank of 6. The majority of those links come from high PageRank pages with few outbound links. It is also likely that when a website has a vast number of backlinks but low PageRank that the majority of the links it is receiving have little if any value. 구글광고대행
3 The value of a backlink is probably modified by the relevance of the linking page.
4 PageRank information provided by Google is in integers but we know that Google uses several decimal points.
5 PageRank information made available to us is at least three months out of date.
How can we use this information in our SEO campaigns?
An essential concept in SEO is keyword difficulty – the difficulty of achieving top positioning for a keyword. It is apparent that backlink numbers have little meaning in terms of total link juice going to a website or web page. We do not know exactly how PageRank is calculated but we should accept Google’s statement that “PageRank is Google’s view of the importance of this page.” The best modality for determining keyword difficulty is PageRank.