Responsive iframe: http://maddesigns.de/responsive-iframes-2417.html
.embed-container {
position: relative;
padding-bottom: 56.25%; /* ratio 16x9 */
height: 0;
overflow: hidden;
width: 100%;
height: auto;
}
.embed-container iframe {
position: absolute;
top: 0;
left: 0;
width: 100%;
height: 100%;
}
/* ratio 4x3 */
.embed-container.ratio4x3 {
padding-bottom: 75%;
}