Modal dialogs can enhance usability by focusing attention on a specific message that requires a user action to continue.

An accessible modal dialog is one where keyboard focus is managed properly, and the correct information is exposed to screen readers. HTML and WAI-ARIA can be used to provide the necessary semantic information, CSS the appearance and Javascript the behavior.

Expandables (sometimes called “collapsible” or “disclosure widgets”) are simple interface patterns that allow you to expand and collapse content. They can be helpful accessibility aids as they give users the choice of revealing content to read it, or bypassing the content, making page navigation more efficient for screen-reader users and people using the keyboard or alternative input devices.

To ensure that they are accessible, it's important that expandable sections are coded so that their state (...

Interactive elements should, under most circumstances, be focusable in the order that they appear in the source code. This helps people who are using the keyboard or alternative input devices to follow focus in a logical order.

The order that elements appear in the document source should reflect the order they appear visually.

Sometimes, design requirements mean that you need to create an interactive element from a base <div> element or a custom element like <my-button> rather than using a native HTML element.

Your element will not be accessible by keyboard unless it is included in focus order and it can be activated using the ENTER and SPACE keys.

Visually indicating which element has focus is important for effective keyboard navigation. It's also important to ensure that only those elements that are available visually for interaction are focusable. If an active element is intended to be unavailable in a particular state and it’s hidden from view, it should not be able to receive focus.

Having to tab through invisible controls to reach visible ones is arduous and potentially confusing for sighted users navigating the page by keyboard. Also, screen-...

Links (<a> elements) are focusable by default, so it should normally be possible to activate them using the keyboard. However, under certain circumstances, they are not focusable: Unless you are deliberately trying to "disable" a link, make sure it does not take the form of any of these examples.