html { font-size: 100%; -webkit-text-size-adjust: 100%; -ms-text-size-adjust: 100%; background: transparent; }
body { margin: 0; padding: 0; background: transparent;}
.video480p {
    margin: 0 auto;
    width: 850px;
}
.video720p {
    margin: 0 auto;
    width: 1280px;
}