I'm currently trying to customize OpenCms (java-based open source CMS) a bit, which is using the FCKEditor embedded, which is what I'm trying access using js / jQuery.

I try to fetch the html content of the iframe, however, always getting null as a return.
This is how I try to fetch the html content from the iframe:

var editFrame = document.getElementById('ta_OpenCmsHtml.LargeNews_1_.Teaser_1_.0___Frame');

alert( $(editFrame).attr('id') );         // returns the correct id

alert( $(editFrame).contents().html() );  // returns null (!!)

Looking at the screenshot, the what I want to access is the 'LargeNews1/Teaser' html section, which currently holds the values Newsline en....
Below you can also see the html structure in Firebug.

However, $(editFrame).contents().html() returns null and I can't figure out why, whereas $(editFrame).attr('id') returns the correct id.

The iframe content / FCKEditor is on the same site/domain, no cross-site issues.

HTML code of iframe is at http://pastebin.com/hPuM7VUz

Updated:

Here's a solution that works:

var editArea = document.getElementById('ta_OpenCmsHtml.LargeNews_1_.Teaser_1_.0___Frame').contentWindow.document.getElementById('xEditingArea');                        

$(editArea).find('iframe:first').contents().find('html:first').find('body:first').html('some <b>new</b><br/> value');