function mainmenu() {
  $(" #nav ul ").css({ display: "none" }); // Opera Fix
  $(" #nav li").hover(function() {
    $(this).find('ul:first:hidden').css({ visibility: "visible", display: "none" }).show(400);
  }, function() {
    $(this).find('ul:first').css({ visibility: "hidden" });
  });
}

$(document).ready(function() {
  mainmenu();
});