/* The styles for the operation of the 2-tier navigation menu */
#nav_menu ul {
	display: flex;
	justify-content: space-between;
	position: relative;    /* So the first submenu can be positioned within the main menu */
	max-width: 2400px;
}
#nav_menu ul li {
	float: left;
}
#nav_menu ul ul {
	display: none;         /* Don't display submenu until hover of the li element */
	position: absolute;
	top: 100%;             /* Position the submenu at the bottom of the main menu */
}
#nav_menu ul ul li {
	float: none;           /* Display the submenus vertically */
}
#nav_menu ul li:hover > ul {
	display: block;        /* Display the submenu on hover of the li element */
}
#nav_menu > ul::after {
	content: "";
	display: block;
	clear: both;
}

/* The styles for the formatting of the 2-tier navigation menu */
#nav_menu ul {
	margin: 0;
	padding: 0;
}
#nav_menu ul li a {
	text-align: center;
	display: block;
	width: 120px;
	padding: 1em 0;
	text-decoration: none;
	background-color: gray;
	color: black;
	font-weight: bold;
}
#nav_menu ul li.lastitem a {
	width: flex;               /* So the menu fills the 706px width of the page */
}
#nav_menu ul li a.current {
	color: yellow;
}
#nav_menu ul li a:hover, #nav_menu ul li a:focus {
	background-color: blue;
	color: white;
}