Edit in JSFiddle

function labnolThumb(e){return'<img class="youtube-thumb" src="//i.ytimg.com/vi/'+e+'/hqdefault.jpg"><div class="play-button"></div>'}function labnolIframe(){var e=document.createElement("iframe");e.setAttribute("src","//www.youtube.com/embed/"+this.parentNode.dataset.id+"?autoplay=1&autohide=2&border=0&wmode=opaque&enablejsapi=1&controls=0&showinfo=0"),e.setAttribute("frameborder","0"),e.setAttribute("id","youtube-iframe"),this.parentNode.replaceChild(e,this)}!function(){for(var e=document.getElementsByClassName("youtube-player"),t=0;t<e.length;t++){var a=document.createElement("div");a.innerHTML=labnolThumb(e[t].dataset.id),a.onclick=labnolIframe,e[t].appendChild(a)}}();
<div class="youtube-container">
  <div class="youtube-player" data-id="1da0ZBZH40o"></div>
</div>
.youtube-container{display:block;margin:20px auto;width:100%;max-width:600px}.youtube-player{padding-bottom:56.25%;overflow:hidden;position:relative;width:100%;height:100%;cursor:hand;cursor:pointer;display:block}img.youtube-thumb{bottom:0;display:block!important;left:0;margin:auto!important;max-width:100%!important;width:100%!important;position:absolute;right:0;top:0;height:auto!important}div.play-button{height:72px;width:72px;left:50%;top:50%;margin-left:-36px;margin-top:-36px;position:absolute;background:url(http://i.imgur.com/TxzC70f.png) no-repeat}#youtube-iframe{width:100%;height:100%;position:absolute;top:0;left:0}