twitter/bootstrap — pull request #3052 by Barryvdh (2012-04-13 11:01:57+00:00)
Title: jQuery Fallback for unsupported CSS transitions (IE7/IE8/IE9)

This commit provides a jQuery fallback, used when css transitions are not available.

It also changes carousel.less, because of an issue with the image dissapearing in IE7 (with this fallback).

I don't know if this is the fastest/best way, but it seems to be working on the sites I've tried it (and it is better then no transition..)
(As reported in Issue #2726)