.videowrapper {
    float: none;
    clear: both;
    width: 100%;
    position: relative;
    padding-bottom: 56.25%;
    padding-top: 0px;
    height: 0;
}
.videowrapper iframe {
    position: absolute;
    top: 0;
    left: 0;
    width: 99%;
    height: 99%;
}