Most links and buttons in the admin don’t have clear :focus and :active styling. This is a big problem when using the Tab key to navigate. There is usually no indication of what element is focused and if there is some, like on the admin menu, it’s quite weak/unnoticeable.
Thinking we should add clear and visible styles for :focus and :active everywhere by default. If this is impossible to do without making the UI “ugly”, can add another global screen option “Enhanced Accessibility” or similar that would turn these styles on.
Pinging all designers, if you come up with a nice solution, please add a screenshot (and possibly a patch) to ticket 21324.