Something definitely is different with buttons. No exception for buttons is described here: https://developer.mozilla.org/en-US/docs/Web/CSS/:hover I notice when I right-click > Inspect Element (Q) on the various spans in the button, that Firefox detects the button element as the right-clicked element. If I add an onmouseover handler to one of the child nodes of the button, it doesn't fire on mouseover. So it seems that mouse events do not pass through the button to its child nodes. Perhaps that is the reason that the hover state is not activated? You could consider filing a bug to see whether this can be fixed or is the intended behavior: https://bugzilla.mozilla.org/ ''Edit: I tested using my regular setup including NoScript. This should be verified in a "clean" profile.''