emmetio/emmet — pull request #120 by akella (2012-11-20 20:12:34+00:00)
Title: br, bl, bb, bt abbreviations for css 

br -> border-right
bl -> border-left
bt -> border-top
bb -> border-bottom

They are safe (not used in Emmet before). I left bdl, bdr and anothers just to stay safe with old users