.board4_body iframe {
	width:100%;
	height:600px;
}
@media screen and (max-width: 900px) {
	.board4_body iframe {
		height:540px;
	}
}
@media screen and (max-width: 800px) {
	.board4_body iframe {
		height:480px;
	}
}
@media screen and (max-width: 700px) {
	.board4_body iframe {
		height:420px;
	}
}
@media screen and (max-width: 600px) {
	.board4_body iframe {
		height:360px;
	}
}
@media screen and (max-width: 500px) {
	.board4_body iframe {
		height:300px;
	}
}