gistfile1.txt

// Create a file on your desktop, enter the code, and then open it LOCALLY in your browser

// This works...
var http = new XMLHttpRequest();
var url = "http://www.need-a-real-url.com";
var params = "<data></data>";
http.open("POST", url, true);
http.send(params);

// This doesn't...
var http = new XMLHttpRequest();
var url = "http://www.need-a-real-url.com";
var params = "<data></data>";
http.open("POST", url, true);
http.setRequestHeader('Content-Type', 'application/xml');
http.send(params);