.sehife{
        width:100%;
        min-height:100%;
        background-color: #d9f9d1;
        border-radius: 2px;
        border-color: black;
        border: 5px;
        float: left;

}


.ratio-16x9 {
    position: relative;
    width: 100%;
    padding-bottom: 56.25%;
    height: 0;
    margin-bottom: 10px;
}
.ratio-16x9 iframe {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
}




footer {
  background-color: #777;
  padding: 10px;
  text-align: center;
  color: white;
}