Another aspect of proper accessibility that's very important for screen readers and SEO is the structure of the HTML on the page.

We normally refer to this structure as "cascading headers". This means that your HTML follows the proper formatting flow, starting with an H1, then H2, then H3, and so on. Headers should be treated as such, as well, and not used to display what grammatically should be a paragraph. For example, after your page title (H1), you may want an overview of your page that summarizes its purpose. You would use a paragraph for this and not an H2 as it would not be considered an actual header.