IE9 do not animates accordion

[poul-kg]

Issue: IE9 do not animates accordion
My environment: Windows 7 64bit / Internet Explorer 9.0.8112.16421 64-bit edition

Steps to reproduce:

1. Visit URL: http://twitter.github.com/bootstrap/javascript.html#collapse
2. Click Collapsible Group Item Use a simpler clearfix #2, then Collapsible Group Item adding o/ms gradient and unprefixed one #1
3. Accortion is not animated

Animation works fine in Google Chrome and Firefox

[owenversteeg]

I think this is a duplicate of the other issue you opened; IMHO, opening one bug for each browser would result in a crapload of issues.

[mdo]

IE9 doesn't support transitions like Chrome and Firefox. Nothing we can do here about this—it's a progressive enhancement.