Sort of.  The CSS rule is `opacity: 0` except on hover, which is `opacity: 1`.  This rule however is applied directly to the element, which overrides the default `opacity: 0` rule.  Basically, it makes the close box visible when hovering over the entire breadcrumb, rather than just over the close box itself.

This could be implemented using the [subject indicator (parent) selector](http://www.w3.org/TR/selectors4/#subject) in CSS4, but there isn't a browser in the wild that supports it yet.