Use the JavaScript console in Firebug and run the following script snippet: var xmlhttp = new XMLHttpRequest(); xmlhttp.open(“HEAD”, “the_url”,true); // Async HEAD request (relative path to avoid cross-domain restrictions) xmlhttp.onreadystatechange=function() { if (xmlhttp.readyState==4) { // make sure the request is complete alert(xmlhttp.getAllResponseHeaders()) // display the headers } } xmlhttp.send(null); // send request