Hover doesn't work on nested ul in ie9
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I have [this website](http://alcappellorosso.it/) where on the left menu there's a nested menu on the "hotel" link. The submenu that appears hovering "hotel" has a gap on the left, but since in the gap the mouse hovers the nested "ul" element there are no problems in Firefox or Google Chrome. But this doesn't work in IE9 (not sure about other versions), infact I can't reach the submenu because it disappears.

Is this a known bug? Am I doing something wrong?