Is CSS under-specified? when I've been curious about some thing, there has been a pretty detailed spec. There are differences in behavior on newer things as thi

Is CSS under-specified? when I've been curious about some thing, there has been a pretty detailed spec. There are differences in behavior on newer things as things get worked out, but I feel like so much is due to actual bugs relative to the spec than the spec itself. Is there an example of under-specification that sticks around in practice?