var req;
var place;

function retrieveURL(url, target) {
    place = target;
    if (window.XMLHttpRequest) { // Non-IE browsers
        req = new XMLHttpRequest();
        req.onreadystatechange = processStateChange;
        try {
            req.open("GET", url, true);
        } catch (e) {
        alert(e);
    }
    req.send(null);
    } else if (window.ActiveXObject) { // IE
        req = new ActiveXObject("Msxml2.XMLHTTP");
        if (req) {
            req.setRequestHeader('Content-Type','text/html');
            req.onreadystatechange = processStateChange;
            req.open("GET", url, true);
            req.send();
        }
    }
}

function processStateChange() {
    if (req.readyState == 4) { // Complete
        if (req.status == 200) { // OK response
            document.getElementById(place).innerHTML = req.responseText;
        } else {
            alert("Problem: " + req.statusText);
        }
    }
}