_includes/youtube.html
<div class="embed-container">
<iframe width="640" height="390"
src="https://www.youtube.com/embed/{{ include.id }}"
frameborder="0" allowfullscreen></iframe>
</div>
<style>
.embed-container {
position: relative;
padding-bottom: 56.25%;
height: 0;
overflow: hidden;
max-width: 100%;
}
.embed-container iframe,
.embed-container object,
.embed-container embed {
position: absolute;
top: 0;
left: 0;
width: 100%;
height: 100%;
}
</style>