function getHTTPObject() {
        var xmlhttp;
        if(window.XMLHttpRequest){
                xmlhttp = new XMLHttpRequest();
        } else if (window.ActiveXObject){
                xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
                if (!xmlhttp){
                        xmlhttp=new ActiveXObject("Msxml2.XMLHTTP");
                }
        }
        return xmlhttp;
}

var http = getHTTPObject();