Steps to reproduce:
1) Go to the URL
2) Click the light blue div that is supposed to spin when clicked
3) Hover over the dark red div that is supposed to get a thicker blue border
The light blue div does not spin, and while the red div's border animates, it animates inwards instead of outwards, as if the box-sizing mode is wrong.
Behaves correctly in Safari 3.2.1 on Windows, behaves correctly in TOT on Mac. Broken in TOT on Windows.
My guess is that this might have to do with MSVC's different behavior with enums in bitfields.
For what it's worth, this bug is also present in a ToT build of Windows Cairo. As this is also built with Visual Studio, it probably is due to the same cause.
I thought this might help corroborate the theory that Visual Studio is to blame.
If you load the blog post and scroll down without hovering over the first animation example, the third one's blue border grows properly. Also, after you click on the second example, if you force a relayout (NOT just a repaint) by adjusting the window size, the animation "unsticks" and is carried out.
FWIW this seems to work properly in the latest Chrome nightly (6116 - http://build.chromium.org/buildbot/snapshots/chromium-rel-xp/) which, if I've poked around their tree properly, appears to use WebKit r38729 (http://src.chromium.org/svn/trunk/src/WEBKIT_MERGE_REVISION).
Works with WebKit commit 38878. Please retry with this version or later.