Pixels in CSS do mean something, which is very clearly defined and which does related in a natural way to what a physical pixel would have been at the time. It'

Pixels in CSS do mean something, which is very clearly defined and which does related in a natural way to what a physical pixel would have been at the time. It's just that the definition adapts in a useful way to modern equipment as well, so dimensions specified in px for older screens still look roughly the same on newer ones.