$(function() {
			//We initially hide the all dropdown menus
			$('#dropdown_nav li').find('.sub_nav').hide();

			//When hovering over the main nav link we find the dropdown menu to the corresponding link.
			$('#dropdown_nav li').hover(function() {
				//Find a child of 'this' with a class of .sub_nav and make the beauty fadeIn.
				$(this).find('.sub_nav').fadeIn(100);
			}, function() {
				//Do the same again, only fadeOut this time.
				$(this).find('.sub_nav').fadeOut(50);
			});
		});