Semantic Markup - Semantic Markup is the use of HTML markup to reinforce the semantics, or meaning, of the information in webpages and web applications rather than merely to define tis presentation or look. Semantic HTML is processed by traditional web browsers as well as by many other user agents.
Section 508 is an Amendment of the Rehabilitation Act of 1973 that requires Federal agencies to make their eletronic and information technology to be accessible to those with disabilities, and prohibits discrimination on the basis of disability for entities receiving federal funds.
Search Engine Optimization(SEO) is the process of affecting the visibility of a website or a web page in a web search engine's unpaid results - often referred to as "natural", "organic", or "earned" results. In general, the earlier, and more frequently a site appears in the search result list, the more visitors it will receive from the search engine's users; these visitors can then be converted into customers.
SEO and Section 508 can work together by letting anyone who use computer to view and understand HTML, no matter if they have a disability or not. It also helps them able to search for the website they want to visit. SEO provides the search engine while Section 508 allows people with disabilities to use the search engine to find whatever they are looking for.