Automattic/jetpack — pull request #933 by kraftbj (2014-08-04 02:35:59+00:00)
Title: CSS Tidy: Add Opera prefix for keyframes at rules.

Ref: http://www.opera.com/docs/specs/presto2.11/css/animations/

Reported in http://wordpress.org/support/topic/custom-css-deleting-o-tags?replies=1