Untitled

<!DOCTYPE html>
<html>
<head>
	<link rel="stylesheet" type="text/css" href="hw1.css">
</head>
<body>
	<div>

	</div>

	<div id="container">
		<div class="content">

		<div class="mar acrticle">cột 1</div>
		<div class="mar acrticle">cột 2</div>
		<div class="mar acrticle">cột 3</div>
		<div class="arcticle">cột 4</div>

		</div>
	</div>

</body>
</html>


*{
	box-sizing: border-box;
}
#container{
	display: block;
	width: 800px;
	height: auto;
}

.content{
	display: flex;
	width: 800px;
	height: 400px;
	border: 2px solid blue;
}
.mar{

	margin-right : 30px;
}
.article{
	width: 200px;
	height: 400px;
	background: #b1b1b1;
	border: 1px solid red;
}