How to extract content from an iframe

How to extract content from an iframe

Hi,
at the moment i'm trying to develop a Win8-App using only HTML5/JS
It works perfectly fine, until i want to extract some text from an iframe, i embedded into my "site"...

The code of the iframe:
  1. <iframe name="mainframe" id="contentframe" frameborder="0" height="300" src="http://www.combib.de/losungformat/heute.html#0A57C0#FFFFFF#CCCCCC#F5F5F5#000000#Arial,Helvetica,Geneva,Swiss,SunSans-Regular#10pt#20pt#16pt#8pt#10px#10px#10px#24px#left#bold#none#1#0#1#0#x#x#x#x#x#x#x#x#x#1#1#_blank#ue#lb#x#x#x#x" >
                </iframe>

Its an iframe to a site, that generates some bible-text according to the stylings given in the link...

Now i want to save the text of the two Bible-Parts in variables
To do this, i looked up the markup of the site and i found two classes:
"att" and "ntt"
So my jQuery-Code looks like this:

  1. $(document).ready(function () {
                var attextvar = $("#contentframe p.att").text();
                var nttextvar = $("#contentframe p.ntt").text();
            });


But this doesn't work
How can i extract the two text passages?
Can't i select the classes, because they're generated by the other site?
Already now, thank you for your answers ;)

P.M.