Pop up menu visibility(with javascript)

I’ve designed a menu,but I’ve a problem on controling the visibility of pop up lists.
You can see the same problem in dbai municipality site.(www.dm.gov.ae)
When I move mouse to the other part of form as the menu is visible,it should hide but I can’t do that.Because each time I try to do this by losting focus from list’s header list’s visibility gets false.