ul{

    width:400px;

    height:400px;

    margin:50px auto;

    padding:0;

    list-style:none;

    border-right:1px dashed #ccc;

    border-left:1px dashed #ccc;

}

li{

    float:left;

    box-sizing:border-box;

    width:30%;

    margin-right:5%;

    height:50px;

    margin-bottom:20px;

    border-radius:10px;

    background:#eee;

    border:1px solid #ddd;

    text-align:center;

    line-height:50px;

    font-size:20px;

    font-family:"Tahoma", sans-serif;

    box-shadow:0 2px 4px rgba(0, 0, 0, 0.1);

}

li:nth-child(3n){

    margin-right:0;

    background-color:#5EB95E;

    color:white;

}