// c.f. http://www.informit.com/guides/content.asp?g=xml&seqNum=231&rl=1
fetch = function(elemId, url){
    var destination = document.getElementById(elemId);
    var req = null;
    var processStateChange=function(){
        if (req.readyState == 4){
            if (req.status == 200){
                destination.innerHTML = req.responseText;
            }
            else{
                destination.innerHTML = "Error loading file";
            }
        }
    };

    if (window.XMLHttpRequest){
        req = new XMLHttpRequest();
        req.onreadystatechange = processStateChange;
        req.open("GET", url, true);
        req.send(null);
    }
    else if (window.ActiveXObject) {
        req = new ActiveXObject("Microsoft.XMLHTTP");
        if (req) {
            req.onreadystatechange = processStateChange;
            req.open("GET", url, true);
            req.send();
        }
    }
}