function makeRequest(url) {

    var http_request = false;

    if (window.XMLHttpRequest) { // Mozilla, Safari,...
        http_request = new XMLHttpRequest();
        if (http_request.overrideMimeType) {
            http_request.overrideMimeType('text/plain');
            // Voir la note ci-dessous à propos de cette ligne
        }
    } 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('Abandon :( Impossible de créer une instance 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) {
            //document.write(http_request.responseText);
            document.getElementById('agenda_content').innerHTML = http_request.responseText;
        } 
    }

}

makeRequest('/agenda/agenda_small.php');