A really simple example ...
<iframe id="fred" width="200" height="200"></iframe>
then the following Javascript is run, either inline, part of an event, etc ...
var s = document.getElementById('fred');
s.contentDocument.write("fred rules");
the "contentDocument" is the equivalent of the "document" you get in the main window, so you can make calls against this to set the body, head, any elements inside ... etc.
I've only tested this in IE8, Chrome and Firefox ... so you may want to test in IE6/7 if you have copies available.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…