.mainpage_box {
display: flex;
flex: 1;
margin: 5px;
.mainpage_row {
display: flex;
flex-direction: row;
flex-flow: row wrap;
padding: 0;
margin: 0;
}
.flex-container{
display: -webkit-flex;
display: -moz-flex;
display: flex;
-webkit-justify-content: space-between;
-moz-justify-content: space-between;
justify-content: space-between;
background-color:lightgrey;
margin:30px auto;
}
.flex-item {
background-color:cornflowerblue;
width: 200px;
height:200px;
line-height:200px;
text-align:center;
color: #fff;
font-size:30px;
}