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|What is PageRank and how does it work?
How is the PageRank calculated?
The Random Surfer Model
False of Spoof Pagerank
What means SEO?
History of SEO
Relationship between SEO and Searchengines
Getting discovered by search engines
|What is PageRank and how does it work?|
To get the PageRank explained correctly, we have to start in the early years of the internet. Since the early stages of the world wide web, search engines have developed different methods to rank web pages. Until today, the event of a search phrase within a document is one major factors within ranking techniques of the major search engines and can thereby be weighted by the length of a document (ranking by keyword density) or by its accentuation within a document by HTML tags.
The technique develops and more and more automatic generated web pages flooded the www. To keep the view the concept of link popularity was developed. PageRank is one of the methods Google uses to determine a page’s relevance or importance. This easy idea is the main concept of the GooglePagerank as it is used today.
PR(A) = (1-d) + d (PR(T1)/C(T1) + ... + PR(Tn)/C(Tn))
Note that the PageRanks form a probability distribution over web pages, so the sum of all web pages' PageRanks will be one.
1. PR(Tn) - Each page has a notion of its own self-importance. That’s “PR(T1)” for the first page in the web all the way up to “PR(Tn)” for the last page
First of all, we see that PageRank does not rank web sites as a whole, but is determined for each page individually. Further, the PageRank of page A is recursively defined by the PageRanks of those pages which link to page A.
But attention, not all links are counted by Google. Some links can cause Google to ignore a site, especially because the webmaster can't control which sites link to their site, but they can control which sites they link out to. So check out the site you are linking to, a link to a PR0-site would be unwise for you.
|How is the PageRank calculated?|
|This is where the hole complex gets a little tricky. The PR of each page depends on the PR of the pages pointing to it. But we won’t know what PageRank those pages have until the pages pointing to them have their PR calculated and so on. Sounds like a circle, and indeed, it is a circle.
But Google gives an easy explanation to this:
PageRank or PR(A) can be calculated using a simple iterative algorithm, and corresponds to the principal eigenvector of the normalized link matrix of the web.
That means, that we can just start calculating a page's PR without knowing the PageRank of the pages linking to our page. Sounds weird, but each time we calculate this, we are getting clother to the final value. All we have to do is calculate until the number stops changing much.
|The Random Surfer Model|
In the Google explanations we can find another addition to this algorithm, the so called Random Surfer Model:
|False of Spoof Pagerank|
|While the PR shown is usually accurate for most sites it must be noted that it is also easily manipulated. A current flaw is that any low PageRank page that is redirected, via a 302 server header or a "Refresh" meta tag, to a high PR page causes the lower PR page to acquire the PR of the destination page. In theory a new, PR0 page with no incoming links can be redirected to the Google home page - which is a PR 10 - and by the next PageRank update the PR of the new page will be upgraded to a PR10. This is called spoofing and is a known failing or bug in the system. Any page's PR can be spoofed to a higher or lower number of the webmaster's choice and only Google has access to the real PR of the page.
For SEO purposes webmasters often buy links for their sites. As links from higher PR pages are believed to be more valuable they tend to be more expensive.
|What means SEO?|
|Search engine optimization (SEO) is a set of methods aimed at improving the ranking of a website in search engine listings. The term also refers to an industry of consultants that carry out optimization projects on behalf of clients' sites.
Using search engines, visitors can find sites in a variety of ways: via paid-for advertisements in the search engine results pages (SERPs), via third parties who are listed in the search engines, or via "organic" listings, i.e. the results the search engines present users. SEO is primarily concerned with improving the visibility of a site in the organic search results.
High rankings in the organic search results can provide targeted traffic for a site. Obtaining that traffic by other means can potentially be expensive. For particularly competitive terms, the cost per click can run several dollars, or more, when pay per click advertising or banner advertising are used. For even moderately competitive terms the cost can range from a few cents to several tens of dollars per visitor. Given those costs, it often makes sense for site owners to optimize their sites for organic search..
Other sites target a specific population, with particular needs or interests. Many businesses try to optimize their sites for large numbers of highly specific keywords that indicate a prospective customer who is ready to buy their product. Focusing on desired traffic can generate more high-quality sales leads, and fewer time-wasting inquiries.
|History of SEO|
|SEO began in the mid-1990s, as the first search engines were cataloging the early web. Initially, all a webmaster needed to do was submit a site to the various engines which would run spiders programs to "crawl" the site, and store the collected data. The search engines then sorted the information by topic, and serve results based on pages they had spidered. As the number of documents online kept growing, and more webmasters realised the value of organic search listings, it became imperative for search engines to sort the vast collection of pages they had spidered and display the most relevant pages first. This was the start of a search engine vs. SEO struggle that continues to this day.
Initially, search engines were guided by the webmasters themselves. Early versions of search algorithms relied on webmaster-provided information like meta tags. Meta tags provided a guide to each page's content and relevant keywords. Soon some webmasters began to abuse meta tags, causing their pages to rank for irrelevant searches. In response, search engines developed more complex algorithms, taking into account a wider range of factors, but they still relied largely on what are today known as "on-site" factors. Examples of on-site factors include:
* Keywords in the domain name
The inherent flaw in relying so extensively on that factors was that webmasters and SEOs had full control over them and could "optimize" their pages for better rankings. Search engines had to adapt again to ensure their SERPs showed the most relevant pages rather than the best optimized ones.
A new search engine emerged with a new kind of thinking. Google was started by two PhD students at Stanford University, Sergey Brin and Larry Page, and brought a new concept to ranking web pages. This concept, called PageRank, was, for many years, the mainstay of the Google algorithm. PageRank relied heavily on incoming links and used the logic that each link to a page is a vote for that page's value. The more incoming links a page had the more "worthy" it was. The value of each incoming link itself varied directly based on the PageRank of the page it was coming from and inversely on the number of outgoing links on that page. PageRank proved to be very good at serving relevant results. Google became the most popular and successful search engine. Because PageRank measured an off-site factor, it was more difficult to manipulate - at first.
Given time, and the realization that PageRank was the new game in town, webmasters focused on exchanging, buying, and selling links on a massive scale. PageRank's reliance on the link as a vote of confidence in a page's value was undermined as many webmasters sought to garner links purely to influence Google into sending them more traffic, irrespective of whether the link was useful to human site visitors.
It was time for Google and other search engines to look at a wider range of off-site factors. There were other reasons to develop more intelligent algorithms. The Internet was reaching a vast population of non-technical users who were often unable to use advanced querying techniques to reach the information they were seeking and the sheer volume and complexity of the indexed data was vastly different to the early days. Search engines had to develop predictive, semantic, linguistic and heuristic algorithms.
The PageRank metric itself is still displayed in the Google Toolbar, but it is only one of several factors that Google considers in ranking pages.
Today, most search engines keep their methods and ranking algorithms secret. A search engine may use hundreds of factors in ranking the listings on its SERPs; the factors themselves and the weight each carries may change continually.
Much current SEO thinking on what works and what doesn't is largely speculation and informed guesses. Some SEOs have carried out controlled experiments to guage the effects of different approaches to search optimization.
The following, though, are some of the considerations search engines could be building into their algorithms, and the list of Google patents may give some indication as to what is in the pipeline:
* Age of site
|Relationship between SEO and Searchengines|
|In the early 2000, search engines and SEO firms attempted to establish an unofficial 'truce'. There are several tiers of SEO firms, and the more reputable companies employ content-based optimizations which meet with the search engines' (reluctant) approval. These techniques include improvements to site navigation and copywriting, designed to make websites more intelligible to search engine algorithms.
Search engines have also reached out to the SEO industry, and are frequent sponsors and guests at SEO conferences and seminars. In fact, with the advent of paid inclusion, search engines now have a vested interest in the health of the optimization community.
|Getting discovered by search engines|
|New sites need no longer need to be submitted to search engines to be listed. A simple link from an established site will get the search engines to visit the new site and spider its contents. It is rarely more than a few days from the acquisition of the link to all the main search engine spiders visiting and indexing the new site.
Naturally, this means that it is good practice to have some means (such as a site map, or plain hypertext links) so that once a spider finds part of a site, it can navigate to the rest. Otherwise, individual, isolated, dead-end pages must be found one-by-one from outside the site; any pages that are not linked to from outside can only be found by links internal to the site.
For those search engines, like Yahoo, who have their own paid submission, it may save some time to pay a nominal fee for submission.
So-called "Ethical" methods of SEO involve following the search engines' guidelines as to what is and what isn't acceptable. Their advice generally is to create content for the user, not the search engines; to make that content easily accessible to their spiders; and to not try to game their system. Often webmasters make critical mistakes when designing or setting up their web sites, and "poison" them so that they will not rank well. Ethical SEO attempts to discover and correct mistakes, such as menus not-readible, broken links, temporary redirects, or a generally poor navigation structure that places pages too many clicks from the home page.
* Using a robots.txt file to grant permissions to spiders to access, or avoid, specific files and directories in the site
As search engines operate in a highly automated way it is often possible for webmasters to use methods and tactics not approved by search engines to gain better ranking. These methods often go unnoticed unless an employee from the search engine manually visits the site and notices the activity, or a change in ranking algorithm causes the site to lose the advantage thus gained. Sometimes a company will employ an SEO consultant to evaluate competitor's sites, and report "unethical" optimization methods to the search engines.