duration in toggleClass doesn't work

duration in toggleClass doesn't work

Hi,
I wondering why animation effect doesn't work on demo page
http://jqueryui.com/demos/toggleClass/default.html. I have the same
problem in my project and this is not browser problem. I can see
animation effect on http://jqueryui.com/demos/toggleClass/. Thanks for
help
br
Kris
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