show XML tagnames from extension

"michael" <[email protected]> Sun, 13 May 2007 11:51:20 +0200
Newsgroups gmane.comp.mozilla.devel.xml
Message-ID <[email protected]>
Hello,
I want to do a JavaScript function to obtain the XML tagnames. I don't know 
how I can access to the XML code, I only get the HTML code.

Thank you.