.header{
    background-color: brown;
    height: 20px;
    border: solid black 3px;
}
.container{
    border: solid blue 2px;
    /* 2nd Method */
    /* overflow:hidden; */
}
.childcontent{
    background-color: chocolate;
    width:50px;
    border: solid;
    margin: 3px;
    float: left;
}
.footer{
    background-color: pink;
    height:20px;
    border: solid red 2px;

}

/* 1st Method */
/* .faltu{
    clear: both;
} */


/* Last and Best Method */
.container::after{
    content:" ";
    display:block;
    clear:both;
    *zoom:1;
}