function createRequestObject()
{
    if (window.XMLHttpRequest) {
        try {
            return new XMLHttpRequest();
        } catch (e){}
    } else if (window.ActiveXObject) {
        try {
            return new ActiveXObject('Msxml2.XMLHTTP');
        } catch (e){
            try {
                return new ActiveXObject('Microsoft.XMLHTTP');
            } catch (e){}
        }
    }
    return null;
}