If a link causes something to happen when a user tabs into it, this could be confusing for people with cognitive disabilities or people using assistive technologies, such as screen readers or screen magnifiers. If parts of the webpage must be updated, then then users need to be made aware of what will happen before it occurs.
If a link causes something to happen when a user tabs into it, make sure this is clearly indicated before the link. This can be as simple as a text instruction that says "Opens pop-up menu" or "This will close the current section". If the user will be unable to use the "back" button of their browser to return to the current webpage, make sure this is clearly explained.
No example is available.