*{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}
header{
 background-color: blue;
 padding: 3em;
 color: #fff;
 text-align: center;

}
section>nav{
    float: left;
    width: 30%;
    background-color: burlywood;
    padding: 1.5em;
    height: 250px;
}
section>nav>ul{
    list-style: none;
}
section>nav>ul>li>a{
    text-decoration: none;
    color: #000;
}
article{
    float: left;
    padding: 20px;
    width: 70%;
    /* background-color: aqua; */
}
footer{
    background-color: #ccc;
    padding: 20px;
    text-align: center;

}

.clearfix::after{
    content: '';
    display: block;
    clear: both;
    overflow: hidden;
}

/* 반응형웹  */
@media screen and (max-width:600px) {
    section>nav, article{
        /* background-color: aqua; */
        width: 100%;
        height: auto;
    }
}