// Set path to the iframe file
var filePath = 'http://www.tfl.gov.uk/tfl/syndication/feeds/serviceboard-fullscreen.htm';
var iframe='<iframe id="tfl_serviceboard_stretchy" name="tfl_serviceboard" src ="#" width="100%" height="1" marginheight="0" marginwidth="0" frameborder="no" scrolling="no"></iframe>';
document.write(iframe);

var aspectRatio = 1.1;

var myIframe = parent.document.getElementById("tfl_serviceboard_stretchy");
var iframeWidth = myIframe.clientWidth -2;
myIframe.height = 220;
myIframe.width = 200;

myIframe.src = filePath;
myIframe.style.border = "1px solid #113B92";