function getXMLHttp()
{
    var XMLHttp = null;
    if (window.XMLHttpRequest)
    {
        try
        {
            XMLHttp = new XMLHttpRequest();
        }
        catch (e) {}
    }
    else if (window.ActiveXObject)
    {
        try
        {
            XMLHttp = new ActiveXObject("Msxml2.XMLHTTP");
        }
        catch (e)
        {
            try
            {
                XMLHttp = new ActiveXObject("Microsoft.XMLHTTP");
            }
            catch (e) {}
        }
    }
    return XMLHttp;
}