body {
  margin: 0;
}
iframe {
  height:calc(100vh - 4px);
  width:calc(100vw - 20px);
  box-sizing: border-box;
}

#header-container{
    width:100%;
    /*Set colour of the image Background per client*/
    background-image:url('../images/header-stretch.gif');
    text-align:center;
}

@media only screen and (max-width : 768px) {
    #header-container img{
        width:100%;
    }
}