CSS animations like this are proposed in CSS3 but only heavily implemented in Webkit at the moment. Mozilla has some support, IE is entirely and unsurprisingly lacking.
Mozilla added support recently, and support has been promised in IE10 and the next Opera release. To me, that spells 'web standard'.
Lots of things get promised in IE that don't wind up being very complete, and it'll be quite some time until the IE7/8/9ers fade away.