function GetXmlHttpObject() 
{
    if (window.XMLHttpRequest) 
    {
        // code for IE7+, Firefox, Chrome, Opera, Safari
        return new XMLHttpRequest();
    }
    if (window.ActiveXObject) 
    {
        // code for IE6, IE5
        return new ActiveXObject("Microsoft.XMLHTTP");
    }
    return null;
}