#container, #container2 {
    width: 500px;
    margin: 0 auto;
    height: 500px;
}
#container div, #container2 div{
    background-color: #ccc;
    width: 40%;
    margin: 2%;
    padding: 2%;
    float: left;
    height: 200px;
}
#container div.selected, #container2 div.selected{
    background-color: red;
}