I’ve just learnt about two things in CSS typography, something new and something old.

Firstly in CSS3 there is a new unit called rem which uses em units that are relative to the document root, rather than the element’s parent, which makes things a lot easier. If you use SASS there is also a mixin available to provide a px fallback for older browsers.

And secondly, line-height can be unitless. Who knew? Not me, obviously.