Quick question: I have two sets of controls that occupy the same space on my website (only one of which is visible at any point in time); the first set is visible by default, and the second set can be activated after which it is displayed on top of the first set via CSS positioning. Both sets are siblings in the DOM. What would be the best approach to dynamically remove the "passive" set from the TAB sequence? (Only the visible, active set of controls should be tabbable.)