body {
    width: 80%;
    margin: 0 auto;
    max-width: 500px;
}

h1 {
    text-align: center;
}

.div_recorder {
    text-align:center;
}

.div_player {
    text-align:center;
}

footer{
    width:80%;
    max-width: 500px;
    margin:20px auto;
    padding-top:20px;
    text-align: center;
}

footer:before{
    content:"";
    position:absolute;
    left:0;
    display:block;
    margin-top:-20px;
    width:100%;
    border-top:1px solid #AEAEAE;
}