The aim of search engine optimisation is to get a site to the top of the natural rankings for search terms that are relevant to the site. Being at the top of the search engine rankings for the relevant terms will drive targeted visitors to the site who are more likely to convert, whether it is to fill in a form, request a brochure or make a purchase.
Natural rankings (otherwise referred to as organic) are the results that appear when a term is typed into a search engine’s search box. The web pages are displayed according to relevance using the search engine's algorithm.
Paid rankings (sometimes referred to as sponsored) are advertisements that are displayed along with the natural listings when a user does a search. Rather than using an algorithm to determine how these sites are listed, they are basically displayed with the highest payer being first. A fee is charged per click on the link. These results mention that they are sponsored.
The 100+ factors that affect how a search engine see a site can be broken down into three categories – content, links and technical spec.
On-site Content
In order for a site to rank for a competitive search term it needs to mention the term within its copy on the site.
In the past there was a lot of focus around keyword density and keyword proximity, but you should really focus on creating the content with the user in mind because it is not worth driving the traffic to your site if you are not going to convert it.
Incoming Links
If a site features information, tools, products or something that people may be interested in that is not easily available elsewhere, then other sites may choose to link to it. Google saw this as a way to rank pages in the web, so a large portion of its algorithm is based around incoming link popularity and relevancy.
For more infomation on links browse to the knowledge base.
Technical Spec
The technical spec of the site can affect how effectively a search engine is able to crawl and index your site. If a search engine has difficulty crawling a site then it can miss valuable content that is available deep within the hierarchy of the site.
Use flat html navigation rather than Flash and JavaScript and try to keep your site’s hierarchy as flat as possible, as page value drops the further into a site you go.
A major survey of online consumers in the UK has found that almost 40% receive error messages whilst transacting and 1/3 are unable to complete a transaction on travel sites.