Re: Tabbed Interfaces in CSS

First of all, read User Interface for CSS3 [1]. You'll find in section
5.3.3 a property called "user-select", that defines the selection /
activation behavior for all elements, regardless of event handling
registered on them.
The value "toggle" says that activation (mouse click, enter key press)
should toggle the :checked pseudo-class, using the value of
"toggle-group": if the latter is "none", element is a checkbox, else
it is a radiobutton (only for :checked).

This means that to your proposal you just need to add
"user-select: toggle" in the style for cards
(it may be implied by appearance:card, but I hope no, since it is not
implied by appearance:checkbox or appearance:radiobox currently)

Adding this property would it be a problem for you?
If yes, why?

Giovanni

[1] http://www.w3.org/TR/2000/WD-css3-userint-20000216