In traditional marketing you're looking to define your targeted audience for your business or organisation. In Internet marketing things work in the same way. Unfortunately, with the growing popularity of the Internet in the past years and with the growing number of people building sites, a certain part of the online audience has been overlooked.
The SEOs with white hats conduct legitimate optimising of web pages to make the site come up appropriately in the Search Engine Results Pages (also called SERPs). The back hat SEOs implement tricks to appear high in the results pages even if the web site is not necessarily relevant. The range of tricks is astonishing. But most of the techniques used by white hat SEOs were similar if not identical to the guidelines given by accessibility experts.
One of the main benefits of Web accessibility is that a Website that's more accessible to people is also usually more accessible to search engines. The more accessible your site is to search engines, the more confidently they can guess what the site's about, giving your site a better chance at the top spot in the search engine rankings.