SuperTables: Why does my page not have a level one heading?

ARIA Rule : Page must contain a level-one heading 

Generally, it is a best practice to ensure that the beginning of a pages main content starts with a h1 element, and to ensure that the page contains only one h1 element. However, ARIA Standards also mentions that in case if iframes, the heading can be an <h2> or <h3> so we have added an invisible heading, which tells the screen readers that it is the SuperTables container. Check the Product Guide for more information.