How many times have you gone to your favorite search engine, typed in your keywords and been shown an entire web site as a result? The odds are, never. More and more often I find myself explaining how it’s not your whole site that is indexed, but it’s a bunch of individual pages on your website that are being indexed. This may seem like an insignificant difference or just a wording issue, but I assure you the distinction is an important one to understand and I promise I am not just splitting hairs.
I would think that most people agree that the general function of SEO is “to help web sites rank higher in the search engines”. I submit a more accurate statement would be “to help the pages of a site rank higher in the search engines”. The pages of a web site are indexed and ranked individually, based primarily on their own merits. There are very few factors in the search algorithms that when changed effect a web site on a global scale.