function createRequestObject() {
    var ro;
    var browser = navigator.appName;
    if(browser == "Microsoft Internet Explorer"){
        ro = new ActiveXObject("Microsoft.XMLHTTP");
    }else{
        ro = new XMLHttpRequest();
    }
    return ro;
}

var http = createRequestObject();

function sndReq(url, callback) {
    if (http && http.readyState != 0) {
        http.abort();
    }
    http.open('get', url);
    http.onreadystatechange = callback;
    http.send(null);
}

// sample callback
function handleResponse() {
    if(http.readyState == 4){
        var response = http.responseText; 
        alert(response);
    }
}