Messias o poeta!
<html>
<meta charset="utf-8">
<script>
function changeSrc(){ document.getElementById('demo').src="https://i.maxthon.com/ru-ru.htm";
}
</script>
<iframe id="demo"src="https://i.maxthon.com/ru-ru.htm"width="250"height="300"></iframe>
<input type="button"onclick="changeSrc()"value="vc ś capaz"/>
</html>