error in integrating fckeditor with netscape7

Hi All,
I am getting following error while integrating fckeditor with netscape7
Error: this.DOMDocument has no properties
in fckeditorcode_gecko_2.js.
The code is working fine with internet explorer 6.
If I try to open http://www.fckeditor.net/demo/default.html in netscape 7, it is showing editor but on the local server, it is giving error.
Please help