body{
    margin: 0px;
    background-color: lightblue;
}
.main{
    margin: 0px auto;
    width: 400px;
    height: 400px;
}
.kutu{
    width: 200px;
    height: 200px;
    float: left;
}
.kutu-1{
    background-color: coral;
}
.kutu-2{
    background-color: lightgreen;
}
.kutu-3{
    width: 400px;
    height: 200px;
    background-color: hotpink;

    clear:left;
    clear: both;
}