You should build a website to benefit your users, and any optimization should be geared toward making the user experience better. One of those users is a search engine, which helps other users discover your content. Search Engine Optimization is about helping search engines understand and present content. Your site may be smaller or larger than our example site and offer vastly different content, but the optimization topics we discuss below should apply to sites of all sizes and types. We hope our guide gives you some fresh ideas on how to improve your website, and we'd love to hear your questions, feedback, and success stories in the Google Webmaster Help Forum1.
SEO may generate an adequate return on investment. However, search engines are not paid for organic search traffic, their algorithms change, and there are no guarantees of continued referrals. Due to this lack of guarantees and certainty, a business that relies heavily on search engine traffic can suffer major losses if the search engines stop sending visitors. Search engines can change their algorithms, impacting a website's placement, possibly resulting in a serious loss of traffic. According to Google's CEO, Eric Schmidt, in 2010, Google made over 500 algorithm changes – almost 1.5 per day. It is considered a wise business practice for website operators to liberate themselves from dependence on search engine traffic. In addition to accessibility in terms of web crawlers (addressed above), user web accessibility has become increasingly important for SEO.
While backlinks are still an important factor used by search engines to determine content quality, linkless mentions are given more weight than ever before. This is partially due to the perception is that linkless mentions are more genuine, unlike black hat SEO techniques like paid links. Social media mentions are also playing an increasingly important role in evaluating website quality.
Google used to make much of its ad hoc keyword search functionality available as well, but now the Keyword Planner is behind a paywall in AdWords as a premium feature. Difficulty scores are inspired by the way Google calculates its Competition Score metric in AdWords, though most vendors calculate difficulty using PA and DA numbers correlated with search engine positions, without AdWords data blended in at all. Search Volume is a different matter, and is almost always directly lifted from AdWords. Not to mention keyword suggestions and related keywords data, which in many tools come from Google's Suggest and Autocomplete application programming interfaces (APIs).
The transparency you provide on your website in text and links about who you are, what you do, and how you’re rated on the web or as a business is one way that Google could use (algorithmically and manually) to ‘rate’ your website. Note that Google has a HUGE army of quality raters and at some point they will be on your site if you get a lot of traffic from Google.
The emphasis on tools, meaning plural, is important because there's no one magical way to plop your website atop every single search results page, at least not organically, though there are best practices to do so. If you want to buy a paid search ad spot, then Google AdWords will happily take your money. This will certainly put your website at the top of Google's search results but always with an indicator that yours is a paid position. To win the more valuable and customer-trusted organic search spots (meaning those spots that start below all of those marked with an "Ad" icon), you must have a balanced and comprehensive SEO strategy in place.