Section 508 Trusted Tester Topic 4 is all about keyboard users, which includes Focus visibility.

Half-baked focus states are my personal design ick. Often only buttons get a custom designed focus state (alongside hoved, clicked, disabled states), but all other elements on the page are left with the default browser focus state.

Don’t get me wrong: There is nothing wrong with the default version. Rather the opposite. If the customized version isn’t as well visible as the browser default, the design missed the point of a focus state.