.sb-item{
    float:left;   
    width : 180px;
    display: block;
    height: 200px;
    margin: 5px;
}

.add-button{
    width: 50px;
    height: 50px;
    border-radius: 50px;
    background: crimson;
    color: white;
    display: table-cell;
    vertical-align: middle;
    position: fixed;
    bottom: 100px; /* negative value of footer height */ 
    right : 100px;
    clear:both;
}