Search Engine Optimisation (SEO)

Search engine optimisation (SEO) is a set of techniques designed to help a website appear more prominently in the search results of popular search engines such as Google, Yahoo or MSN. Search engine optimisation methods, and particularly optimisations targeted at Google, are of great interest to many website owners as these optimisation techniques can help to promote a website if it appears high up in the search engine results pages. This leads to improved website traffic and the potential to derive greater revenue from the website.

Search engine optimisation techniques

There are a wide range of search engine optimisation techniques, and webmasters often have quite different views on which SEO tactics are the most useful. In addition, search engines and the algorithms they use are evolving over time as they try to constantly improve in their main aim: to deliver highly relevant search results to users. Search engines also adapt to ensure they are not fooled by deliberate attempts by webmasters to trick them into giving high search engine rankings for web pages that don't actually merit the high ranking. This means that webmasters need to be aware of changes to keep up to date with what search engines view as legitimate search engine optimisation tactics, as well as the "spammy" optimisation techniques that webmasters should avoid using.

How do search engines calculate search rankings?

One difficulty is that the algorithms used by the search engines to determine the ranking of a web page are not published, for obvious reasons. This fact, together with the highly complex nature of the search engine rankings calculation for billions of web pages, makes it difficult for webmasters to be sure exactly how the rankings are calculated by the search engines. Any claims about knowing the details of any of the search engine algorithms should be treated with caution.

It would be nice to have a way to objectively test certain individual factors, to see their effects on the search engine rankings. However this is a difficult task, as it becomes vital to equalise all factors apart from the one you're interested in. In practice, this is difficult (though perhaps not impossible) to do.

So, if we can never find out much detail about how the search engines calculate their rankings, how do we know what to do in terms of website optimisation? Thankfully, the basic ingredients to good search engine optimisation (SEO) are fairly well known. Webmasters will no doubt always discuss the finer details, and argue over which factors are the most important, but the list below gives what I hope is a practical and uncontroversial overview of the main factors that influence a website's position in the search engine results.

Factors affecting search engine ranking

The factors that affect search engine rankings can be divided in a number of ways. One common grouping is into "on-page factors" and "off-page factors". The on-page factors are (not surprisingly) determined by the content on a specific web page, so the webmaster has direct control over these. On-page factors include things like the HTML page title and keyword occurrences. Off-page factors relate mainly to the way other webapges link to the page in question. The number of links to a page, and the anchor text used in the links are some of the key off-page factors. These have a powerful effect on search engine rankings, but are not under the direct control of the webmaster.

The list below summarises the main on-page and off-page search engine ranking factors.

Useful links

Last updated: March 2012