*{
    box-sizing: border-box;
    margin: 0;
    padding: 0;

}
body{
    display: flex;
    flex-direction: column;
}
header {
    background-color:dodgerblue;
    color: #fff;
    text-align: center;
    padding: 20px;
  }

.content-area{
    display: flex;
    flex-grow: 1;
    padding: 1em;
}
.main-content{
    flex-grow: 3;
    padding: 1em;
    background-color: #f8f8f8;
}
.sidebar{
    flex-grow: 1;
    padding: 1em;
    background-color: #e7e7e7;
}
.foother{
    background-color:deeppink;
    color: white;
    padding: 2em;
    text-align: center;
}

@media (max-width: 768px) {
    .content-area {
        flex-direction: column;
    }
}