FBJS and AJAX

My company has recently decided to move towards developing for Facebook and looking to include a RSS feed on a FBML page within a Fan Page.
Now it looks like FB have their own version of JS running called FBJS and I'm trying to start simple by just importing a text file from our server using AJAX and printing out the result.

I keep getting a 404 error though.
Does any one have any idea why?

This is the code I am using...

<script type="text/javascript">
<!--
function General_Refresh(url,div){  
	document.getElementById(div).setTextValue("Loading " + url + "..."); 
	var ajax = new Ajax(); 
	ajax.responseType = Ajax.RAW;
	ajax.ondone = function(data) { 
		document.getElementById(div).setTextValue(data); 
	} 
	
	ajax.onerror = function(e) { 
		document.getElementById(div).setTextValue("Error");
	} 
	
	ajax.post(url);
}
//--> 
</script>
<div id="mydiv"></div>
<a onclick='General_Refresh("http://www.instarentals.com/robots.txt","mydiv");'>Load content</a>

Code (markup):

 

Sorry, I answered my own question.
Cross domain communication.