jquery UI and IE9
Since Internet Explorer 9 was released, I received some negative feedback on one of my sites using with it.
Quick search in Google returned this blog post “IE9, compatibility mode and the META tag“.
Adding the following tag just after HEAD tag, eliminated my problem.
<meta http-equiv="X-UA-Compatible" content="IE=EmulateIE8" >
Note: seems that all sites, where jQuery is used, need to get this tag for compatibility with IE9