If content in the file makes it very difficult or impossible for someone with a disability to use, the Accessibility Checker classifies it as an error.
All non-text content must have alternative text (alt text).
Screen readers speak the alternative text to describe images and other non-text content that users can’t see. Based on the alt text of non-text content, users should understand the purpose and meaning.
Tables must specify column header information.
Users rely on the table headings to understand the content that is subsequently read by the screen reader. Also, assistive technology often uses the table header row to help convey to the user the current cursor location in the table and to provide information that enables the user to navigate the table. Accessible tables and/or blocks of cells have the header box selected or a header row indicated.
All slides must have titles.
Slide titles enable users to navigate within a presentation, including finding and selecting a single slide to immediately go to.
Documents must use heading styles.
Content is organized with headings and/or a Table of Contents (TOC). Headings and TOCs provide structural context to users and enable navigation and easier searching in the document.