<script type="text/javascript" language="javascript">

    var http_request = false;

    function makeRequest(url) {

        http_request = false;

        if (window.XMLHttpRequest) { // Mozilla, Safari,...
            http_request = new XMLHttpRequest();
            if (http_request.overrideMimeType) {
                http_request.overrideMimeType('text/xml');
                // Przeczytaj o tym wierszu poniżej
            }
        } else if (window.ActiveXObject) { // IE
            try {
                http_request = new ActiveXObject("Msxml2.XMLHTTP");
            } catch (e) {
                try {
                    http_request = new ActiveXObject("Microsoft.XMLHTTP");
                } catch (e) {}
            }
        }

        if (!http_request) {
            alert('Poddaję się :( Nie mogę stworzyć instancji obiektu XMLHTTP');
            return false;
        }
        http_request.onreadystatechange = function() { alertContents(http_request); };
        http_request.open('GET', url, true);
        http_request.send(null);

    }

    function alertContents(http_request) {

        if (http_request.readyState == 4) {
            if (http_request.status == 200) {
                var xmldoc = http_request.responseXML;
var root_node = xmldoc.getElementsByTagName('root').item(0);
alert(root_node.firstChild.data);
            } else {
                alert('Wystąpił problem z zapytaniem.');
            }
        }

    }
</script>
<span
    style="cursor: pointer; text-decoration: underline"
    onclick="makeRequest('test.xml')">
        Odpytaj
</span>

// zamiast alert(root_node.firstChild.data);
// wstaw ten kod:

TuPokaz = document.getElementById("tutaj");
TuPokaz.innerHTML = root_node.firstChild.data;

// w kodzie HTML umieść:
<div id="tutaj"></div>