function createRequestObject()
{
    if (window.XMLHttpRequest) { // Mozilla, Safari, Opera...
        var xmlhttp = new XMLHttpRequest();
        if (xmlhttp.overrideMimeType)
         xmlhttp.overrideMimeType('text/xml');
    }
   else if (window.ActiveXObject)
   { // IE
        try {
            var xmlhttp = new ActiveXObject("Msxml2.XMLHTTP");
        } catch (e) {
            try {
                var xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
            } catch (e) {}
        }
    }

    if (!xmlhttp) {
        alert('Giving up. Cannot create an XMLHTTP instance');
        return false;
    }
   return xmlhttp;
}