Great overview on when/when not to use the
tabindex attribute. Most of it feels like common sense, but the recommendation for
overflow content is an interesting one I'd not come across before:
tabindex="0"should be applied to any non-interactive element that has had CSS’
overflowproperty applied to it. This will allow people using a keyboard to navigate to, and scroll around the overflowed content.
Though don't forget other accessibility requirements, like labels.