font-baseline

see: http://stackoverflow.com/questions/23247467/how-css-line-height-is-measured

http://blog.typekit.com/2010/07/14/font-metrics-and-vertical-space-in-css/

http://static.zealous-studios.co.uk/projects/web_tests/line box.xhtml

http://jeffyam.com/node/189

https://mudcu.be/journal/2011/01/html5-typographic-metrics/#baselineCSS

http://dev.labs.ft.com/george/baseline/