header{
    text-align: center;
    height: 50px;
    background-color: greenyellow;
}

aside{
    background-color:aqua;
}

button{
    border-radius: 40%;
}

button a{
    text-decoration: none;
}

caption, th, td{
    border: 1px solid black;
}

div{
    width: 500px;
}

footer{
    background-color: black;
    width: 100%;
    height: 120px;
    color: white;
    text-align: center;
}