Semantic markup is when you use tags to descibe the type of content when coding. For instance, sections, spanners, headers, bodies, footers, etc. h1 is used for header and ul for unordered. This utilization of HTML markup is helpful in maintaining the semantics and data on sites by being able to clearly display and send information.
The United States Workforce Rehabilitation Act of 1972 was added to Section 508, which stated that any federal electronic and data innovation created, should be accessible to diabled users. This was to prevent discrimination from people with disabilities in the workforce related to the United States government.
Search Engine Optimazation is the process for how visible a website is through a serch engine's result. It starts off by the search terms that are entered into the database and then goes to the common search terms. The more the term is searched, the more likely it shows up to a specific website. The sites are then placed by how many of the terms it encompasses and by how many other wesbites can be linked to this specific site.
Semantic markup, section 508 accessibility and search engine optimazation can all be related through the fact that they are all intact in order to provide betterment for usage of computers and the web. They are created to improve and provide the best service possible to the end users.