Использовать flexbox:
.container {
display: -webkit-flex;
display: flex;
-webkit-flex-direction: row;
flex-direction: row;
-webkit-justify-content: flex-start;
justify-content: flex-start;
flex-wrap:wrap;
}
.block {
background-color: #ddd;
border:1px solid #999;
display: inline-block;
height: 100px;
margin: 4px 2px;
width: 100px;
}
Готово.