Introduction to Search Engines 4

2.4 Ranking

Algorithms
Search providers use complex mathematical equations called algorithms to rank web pages. These algorithms make calculations about the relevance of words on web pages in relation to search queries or the perceived importance and link popularity of websites. They may also take other factors into account when ranking results, such as the age of the domain your site is on, or whether the terms used in a search query appear in the URLs of sites in the search engine’s index.

You may be surprised to learn that SEO professionals are not entirely sure how these algorithms work. In fact, search algorithms are a closely guarded trade secret. If they were made available to the public, we would see a lot more websites trying to find ways to exploit them in order to gain better search engine rankings.

Algorithms tend to be patented, and these patents can sometimes give SEO professionals a clue as to how search engines rank the relevance and importance of web pages. Otherwise, SEO involves a fair degree of trial and error, and most of the SEO process falls back upon tried and tested methods that circulate amongst the SEO community and that have been shown to be effective in improving search engine visibility (SEO websites and forums can be a good place to visit to see SEO professionals discussing these methods and exchanging ideas).

2.4.1 Page Importance

There are two main factors that search engines use to determine the position that pages will gain in search results:

Keyword relevancy
Page importance or link popularity

As we noted above, when you carry out a search query, the search engine tries to return relevant pages for that query by returning pages that contain the keywords in your search query.

However, search engines also take the importance of the page into account when ranking pages. This importance is based on the number of external links pointing to a page. The more links pointing to your pages, the more important they are deemed to be by the search engine.

The best example of this system of ranking pages is Google’s patented PageRank.

2.5 Google PageRank

Google’s PageRank is a system that rates the importance of pages in direct proportion to the number of external links pointing to that page.

PageRank exploits the network of links on the web in order to determine the relative value of individual web pages. It does this by counting the number of links pointing to one page from other sites. As Google puts it, a link to one of your pages from another site is considered a ‘vote’ in favour of that page. The higher the votes, the greater the value or perceived importance of the page.

However, Google also takes the importance of the page that links to your page into account when determining the value of your page. If the page that links to you is already seen to have a high importance –in other words, if it already has a high PageRank – then the link it provides is ‘weighted’ higher than a link coming from a page with a lower PageRank or lesser importance.

Google then combines PageRank with page relevance to ensure that the pages returned in results are not only important in themselves but are also relevant to your search.

You can find Google’s own explanation of PageRank here:

http://www.google.com/technology/

Pages Vs Websites

Google PageRank applies to individual pages and not websites as a whole. Pages on the same site will often have a different PageRank.

It is important to note this emphasis on individual pages rather than sites as a whole. Similarly, when we carry out a search in a search engine, the results returned refer to individual pages rather than whole sites. This makes absolute sense from the point of view of the both the search engine and the user. Some pages within a website will usually be more important than others, e.g. the homepage. Also individual pages within websites are not always relevant to the same things and may cover topics that are unrelated to user’s search query.

From an SEO point of view, you will be looking to optimise individual pages so that they rank for different keywords. We will show you effective methods of achieving this later in the course.

Although PageRank is specific to Google, most of the major search engines now use a similar system to determine the position of pages in search results.

2.5.1 How to check PageRank

It is particularly important that you learn how to understand and measure PageRank, as it will play a significant part in your future SEO efforts. The ability to measure PageRank will help you analyse competitor’s web pages and to keep track of how well your own web pages are faring when they are optimised and online.

To measure Google PageRank you must first install the free Google Toolbar into your browser.

2.5.2 Installing the Google Toolbar

To get the toolbar, navigate your browser to the following URL:

http://toolbar.google.com/

Different versions of the toolbar are available for different browsers like Internet Explorer and Firefox. Google should automatically detect which browser you are using and offer a download for the appropriate version.

2.5.3 Measuring PageRank

With the toolbar installed, try browsing the web. As you navigate from page to page, the little bar next to ‘PageRank’ will fill up green as the PageRank for the current page increases and go down as the PageRank for the current page decreases.

To get a more accurate numeric measure of PageRank, hover your mouse over the part of the Toolbar that reads PageRank. A small dialogue box should appear with the following text:

‘PageRank is Google’s measure of the importance of this page (x/10)’

where x is the actual value of the page out of a total of 10. The higher the number, the higher the PageRank for that page.

You can now measure the PageRank of web pages. This has many SEO applications, including:

The ability to measure the PageRank of your own pages
The ability to measure the PageRank of competitor’s web pages
The ability to measure the PageRank of potential link partners. Remember that the more important the site that links to you is, the more weight is given to that link, hence the greater your perceived importance.

TASK 1: MEASURING PAGE RANK

Let’s try measuring the PageRank of some web pages:

Install the Google Toolbar into your browser, making sure that you enable advanced options.
Once installed, try carrying out a search for the kind of products or services that your website offers.
Visit all the pages returned on the first page of search engine results, and note down their PageRank.
Compare the PageRank of these pages. Which pages have the highest measure of importance and which the lowest?

SUMMARY:

Search engines allow us to search the web by entering search queries that the search engine compares against its index of web pages.
The leading search engines are currently Google, Yahoo, and MSN.

Crawler-based search engines use software called spiders to crawl the web and index web pages.
Search engines use complex mathematical algorithms to rank web pages.
Search engine ranking is based on a combination of page relevance and page importance.
Page importance (or PageRank) is based on the link popularity of a web page and the quantity and quality of external links pointing to that page.
PageRank is calculated on a per-page basis and does not apply to websites as a whole.

For more information about our Search Engine Optimisation Training Courses contact Syllabus or call +34 693 475 142.