Transparency on a SWFobject

Hi There

I am wandering if anyone could help. I have a flash SWFObject on a pafge and i want to make the background transparent so that the base HTML background shows through. This is my code:

var so = new SWFObject(“images/topnav.swf”, “flash”, “100%”, “100%”, “6”,"#000000");
so.addVariable(“xml”, “data.xml?time=”+new Date().getTime())
so.write(“flashcontent”);

where do I add the parameter code and what does the actual code look like?