[Javascript] 'Permission denied to get property HTMLDocument.write' error in Firefox

[ivan at textzi.net (ivan lópez)]

dear list,

I'm updating my vanity site and have run into some trouble with 
Firefox. Any ideas on what I'm doing wrong are appreciated : )

this is what I'm working on:

http://textzi.net/test/

Click the 'click' link. Then direct your browser to any place that 
takes you outside of the frame set-up. Then go back to my page with the 
'back' button of your browser.

This works fine with the browsers I've tested (Safari, Opera, 
Explorer), except Firefox. It disables the 'click' link and, if the 
link is pressed, it throws the following error:

Error: uncaught exception: Permission denied to get property 
HTMLDocument.write

The script that's triggered by the 'click' link is a bit long. 
Basically, it uses the document.write method to nest frames in the top 
frame.

In advance, thanks,

ivan