          var anHttpRequest = new XMLHttpRequest();
            anHttpRequest.onreadystatechange = function() { 
                if (anHttpRequest.readyState == 4 && anHttpRequest.status == 200)
                    aCallback(anHttpRequest.responseText);
            }

            anHttpRequest.open( "GET", aUrl, true );            
            anHttpRequest.send( null );
        }
    }
    
    function add_category(content, last) {
        var step = document.createElement('div');
        step.className =