user agent :focus style breaks tab metaphor

At least in Firefox and Chromium clicking a tab gives it :focus and the user agent style creates an outline for this. Thus a freshly selected Tab has a line around it and implicitly - and most importantly - below it. This breaks the tab metaphor which only works flawlessly, when there is no separator between the active tab and the respective content area. This CSS snippet fixes the problem:

.ui-tabs-active.ui-state-focus, .ui-tabs-active.ui-state-focus * {outline: none 0;}