body{
    box-sizing: border-box;
}
.kontejner{
    background-color: aquamarine;
    width: 960px;
    margin: 0 auto;
    border: 15px darkcyan;

}

.kutije{
    background-color: aqua;
    width: 300px;
    height: 150px;
    outline: 15px black;
    border: 15px darkcyan;
}