1、justify-content属性决定了水平方向子项的对齐和分布方式。

2、应用在弹性容器上，把弹性项沿着弹性容器的主轴线（main axis）对齐。该操作发生在弹性长度以及自动边距被确定后。

css justify-content 实例

.box{
    display:-webkit-flex;
    display:flex;
    width:400px;
    height:100px;
    margin:0;
    padding:0;
    border-radius:5px;
    list-style:none;
    background-color:#eee;
}
.box li{
    margin:5px;
    padding:10px;
    border-radius:5px;
    background:#aaa;
    text-align:center;
}
#box{
    -webkit-justify-content:flex-start;
    justify-content:flex-start;
}
#box2{
    -webkit-justify-content:flex-end;
    justify-content:flex-end;
}
#box3{
    -webkit-justify-content:center;
    justify-content:center;
}
#box4{
    -webkit-justify-content:space-between;
    justify-content:space-between;
}
#box5{
    -webkit-justify-content:space-around;
    justify-content:space-around;
}