I think I may have a better solution for having a fully responsive iframe (a vimeo video in my case) embed on your site. Nest the iframe in a div. Give them the following styles:
div {
width: 100%;
height: 0;
padding-bottom: 56%; /* Change this till it fits the dimensions of your video */
position: relative;
}
div iframe {
width: 100%;
height: 100%;
position: absolute;
display: block;
top: 0;
left: 0;
}
Just did it now for a client, and it seems to be working: http://themilkrunsa.co.za/