Problem with drop down menus on iPad

I’ve encountered a problem with drop down menus on the Unite site when viewed on an iPad (but works fine on the PC and mobile phone). Although the drop down menu is activated when selected, the sub-menus are hidden behind the slider images (when on the home page) or are mixed in with text on other pages (making the sub menus inactive). I’ve checked this on the Unite Demo site and get the same problem. Any help would be much appreciated! Thanks for a great theme.