<div id="isi">
  <div style="background-color:green;"></div>
  <div style="background-color:blue"></div>
  <div style="background-color:red;"></div>
  <div style="background-color:yellow;"></div>
</div>

#isi {
    width: 400px;
    height: 150px;
    border: 2px solid red;
    display: -webkit-flex; /* Safari */
    -webkit-justify-content: space-around; /* Safari 6.1+ */
    display: flex;
    justify-content: space-around;
}

#isi div {
    width: 70px;
    height: 70px;
}