Delay dropped-down menu hide by a few milliseconds, instead of just relying on CSS :hover. **Change main selector.**

Delay dropped-down menu hide by a few milliseconds.js

$(document).ready(function() {
  $('#header-main-menu li').hover(function() {
    // Stop the timer.
    clearTimeout(this.sfTimer);
    // Display child lists.
    $('> ul', this).css({left: 'auto', display: 'block'})
      // Immediately hide nephew lists.
      .parent().siblings('li').children('ul').css({left: '-999em', display: 'none'})
  }, function() {
    // Start the timer.
    var uls = $('> ul', this);
    this.sfTimer = setTimeout(function() {
      uls.css({left: '-999em', display: 'none'});
    }, 400);
  });
});