style.css

body{
    margin-top:70px;
    background:#333;
    color:#fff;
    overflow: scroll;
  }

  .dropbtn {
    background-color: #3498DB;
    color: white;
    padding: 16px;
    font-size: 16px;
    border: none;
    cursor: pointer;
    border-radius: 5px;
    margin-bottom: 15px;
    width: 240%;
}

.dropbtn:hover, .dropbtn:focus {
    background-color: #2980B9;
}

.dropdown {
    position: relative;
    display: inline-block;
}

.dropdown-content {
    display: none;
    position: absolute;
    background-color: #f1f1f1;
    min-width: 160px;
    overflow: auto;
    box-shadow: 0px 8px 16px 0px rgba(0,0,0,0.2);
    z-index: 1;
    width: 240%;
    border-radius: 5px;
}

.dropdown-content a {
    color: black;
    padding: 12px 16px;
    text-decoration: none;
    display: block;
}

.dropdown a:hover {background-color: #ddd}

.show {display:block;}