These criteria are specific for any HTML content.
Given I am a keyboard user, when I encounter interactive content, then I can control it solely from the keyboard.
Given I am a screen magnifier user, when I trigger a tooltip and move my cursor onto it, then the tooltip content remains visible unless I dismiss it.
Given I use a browser to view web content, when I load a new page, then I can understand the page content from the title.
Given I navigate with a keyboard, when I Tab to links and form controls, then I can locate where I am on the page.
Given I navigate with assistive technology, when I encounter content which looks different, then I can perceive this difference. E.g. heading structure, ordered and unordered lists.
Given I use a screen reader, when I focus on form controls, then I can understand what type of data is required.
Given I use a screen reader, when a visual change occurs on the page, then I can understand the change audibly. E.g. search results displaying while searching, errors displaying after activating submit button.
Given I use browser zoom, when I zoom up to 400%, then I can understand and interact with page content.
Given I use a screen reader, when I encounter a descriptive image, then I can understand the image non-visually.
Given I use mobile devices, when I orientate the screen from portrait to landscape, then I can understand the content when it's reflowed.