.contenedor-youtube {
  display: block;
  margin: 20px auto;
  width: 100%;
  max-width: 680px;
}
.reproductor-youtube {
  display: block;
  width: 100%;
  height: 100%;
  padding-bottom: 56.25%;
  overflow: hidden;
  position: relative;
  cursor: hand;
  cursor: pointer;
}
img.imagen-previa {
   display: block;
   left: 0;
   bottom: 0;
   margin: auto;
   max-width: 100%;
   width: 100%;
   position: absolute;
   right: 0;
   top: 0;
   height: auto
}
div.youtube-play {
   height: 64px;
   width: 64px;
   left: 50%;
   top: 50%;
   margin-left: -36px;
   margin-top: -36px;
   opacity:0.7;
   position: absolute;
   background:   url("youtube-64.png") no-repeat;
}
div.youtube-play:hover{
   opacity:1;
}
#youtube-iframe {
   width: 100%;
   height: 100%;
   position: absolute;
   top: 0;
   left: 0;
}