Answers for "how to edit iframe"

change element in iframe

// so you got an iframe (id="myiframe"). In that page you have an element id="theprice" and you want to change its value
// from the parent page do this in your javascript:
var iframevar = document.getElementById('myiframe');
var elmnt = iframevar.contentWindow.document.getElementById("theprice");
elmnt.innerHTML = theNewPrice;

custom iframe

<iframe width="560" height="315" src="https://www.youtube.com/embed/owsfdh4gxyc" frameborder="0" allowfullscreen></iframe>