body {
	max-width: 1000px;
	margin: 0 auto;
}

header, nav, article, aside, section, footer {
	display: block;
}

#header {
	height: 60px;
	background-color: #20b2aa;
}

#header_title h1 {
	font-style: italic;
	font-size: 2em;
	margin: 6px;
}

#header_title h1 a {
	color: #ffffff;
	text-decoration: none;
}

.nav {
	width: 100%;
	max-width: 1000px;
	height: 40px;
	margin: 0 auto;
	padding: 0;
	display: flex;
}

.nav li {
	position: relative;
	list-style: none;
}

.nav li a {
	display: block;
	width: 250px;
	height: 40px;
	text-align: center;
	color: #fff;
	font-size: 1em;
	line-height: 2.8;
	background: #20b2aa;
	transition: 0.5s;
	text-decoration: none;
	border-right: 1px solid #eee;
	box-sizing: border-box;
}


.nav > li:hover > a {/*layer-1*/
	color: #20b2aa;
	background: #afeeee;
}

.nav > li li:hover > a {/*layer-2*/
	color: #20b2aa;
	background: #afeeee;
}

.nav li ul {
	top: 40px;
	left: -40px;
	position: absolute;
}

.nav li ul li {
	overflow: hidden;
	height: 0;
	transition: 0.2s;
}

.nav li ul li a {
	border-top: 1px solid #eee;
}

.nav li:hover > ul > li {
	overflow: visible;
	height: 40px;
}

	.nav li ul li ul {
		top: 0;
		left: 210px;
	}

	.nav li ul li ul:before {/*layer-2?*/
		position: absolute;
		content: "";
		top: 15px;
		left: 30px;
		border: 5px solid transparent;
		border-left: 5px solid #fff;
	}

	.nav li ul li ul li:hover > a {/*layer-3*/
		color: #20b2aa;
		background: #afeeee;
	}

	.nav li ul li ul.left {
		top: 0;
		left: -190px;
	}

	.nav li ul li ul.left:before,/*layer-2-left?*/
	.nav li ul li ul li ul.left:before {/*layer-3-left?*/
		position: absolute;
		content: "";
		top: 15px;
		left: 190px;
		border: 5px solid transparent;
		border-right: 5px solid #fff;
	}

	.nav li ul li ul.left li:hover > a {/*layer-2-left*/
		color: pink;
		background: #afeeee;
	}

	.nav li ul li ul li ul.left li:hover > a {/*layer-3-left*/
		color: purple;
		background: #afeeee;
	}

main {
	float:left;
}

article {
	width:680px;
}

aside {
	float:left;
	width:280px;
}

h2 {
	color: #20b2aa;
	font-size: 2em;
}

h3 {
	color: #20b2aa;
	font-size: 1.5em;
}

h4 {
	color: #20b2aa;
	font-size: 1em;
}

p.indent{
	text-indent: 1em;
	padding-left: 10px;
	margin: 20px;
}

p.indentb{
	text-indent: -1em;
	padding-left: 10px;
	margin: 20px;
}

p.indentc{
	text-indent: -1em;
	padding-left: 24px;
	margin: 20px;
}

p.center{
	text-align: center;
}

p.right{
	text-align: right;
}

ul {
	list-style: none;
}

.content {
	width: 750px;
	height: 200px;
	background: #eee;
	margin: 0 auto;
	padding: 10px;
	text-align: left;
	box-sizing: border-box;
}

table {
	border-collapse: collapse;
	empty-cells: show;
	border-style: solid;
	border-width: 1px;
	border-color: #20b2aa;
	width: 100%;
}

caption {
	text-align: left;
}

th {
	background-color: #20b2aa;
	color: #ffffff;
	text-align: center;
	border-style: solid;
	border-width: 1px;
	border-color: #cccccc;
}

td {
	border-style: solid;
	border-width: 1px;
	border-color: #20b2aa;
	vertical-align: top;
	padding-left: 0.3em;
	padding-right: 0.3em;
}

tr:nth-child(even) {
	background-color: #afeeee;
}

footer {
	max-width: 1000px;
	height: 24px;
	background-color: #20b2aa;
	color: #ffffff;
	clear: both;
}