[1] 構文解析時?に [CODE(CSS)@en[[[em]]]] に変換されるみたいです。

[2] [CITE[css - What does 1__qem mean? - Stack Overflow]]
( ([TIME[2013-08-27 02:38:35 +09:00]] 版))
<http://stackoverflow.com/questions/7448673/what-does-1-qem-mean>