Edit in JSFiddle

#container {
    width: 100%;
    text-align: center;
    border: 1px solid grey;
}
 
.box {
    display: inline-block;
    width: 250px;
    height: 250px;
    margin: 10px;
    background: lightblue;
}

<div id="container">
	<div class="box"></div>
	<div class="box"></div>
	<div class="box"></div>
</div>