Most of the website structure is Header, navigation, section main content and footer. Unfortunately, the screen reader may have to read the site to its user in that order. Since most sites repeat the same header and navigation on each page, the user will have to hear these elements each time they visit another page.
HTML5 interduce a new role attribute. This lets us assign a “responsibility” to each element on your page. Then the screen reader can very easily parse the page and categorize all of those responsibilities, so that you can create a simple index for the page.