thoughtbot/bourbon — pull request #71 by ubuwaits (2012-03-06 21:52:06+00:00)
Title: Remove -o and -ms vendor prefix definitions from border-radius mixin.

Both IE and Opera support the prefix-less border-radius definition.

Reference:
http://my.opera.com/community/forums/topic.dml?id=651612
http://stackoverflow.com/questions/635851/support-for-border-radius-in-ie