SEO takes into account factors that are both on-site and off-site. On-site SEO entails an analysis of your website. It involves looking at many factors including the site structure, use of keywords, the sites content, page loading times and the HTML and CSS that the site is built with. Good on-site SEO benefits the end user and also helps to avoid any technical “Gotchas” that search engines don’t like, such as duplicate content. Checkout search engine optimisation packages.
A good SEO will start by analysing your site and making recommendations to improve an optimise the site for both users and search engines. Off site SEO involves creating relevant backlinks from other sites to yours.
Each backlink is counted by the search engines as a vote for your site. Websites are given an authority score called Page Rank. Each time a site links to you it shares a little bit of its page rank with you, links from high authority sites share more of this page rank than lower authority sites. Incoming links to a site are known as backlinks.
To Follow or to Nofollow…
Some links carry no authority at all, many links carry a nofollow attribute that tell the search engines not to count that link as a vote. Webmasters and bloggers might add this attribute themselves if they don’t their link to be counted as a vote for the external site or it could be automatically added by the platform they are using to publish their content, this is often the case when a site offers its user to add comments or content and the webmaster has little control over what links get created by the sites contributors.
Links without the nofollow attribute are termed “dofollow” and pass page rank from your page to the linked page. In HTML there is no actual dofollow attribute, dofollow happens by default in the absence of a nofollow attribute. You should never nofollow internal links as this will cause any page rank that would have been passed to that link to just evaporate!