var READYSTATE_UNINITIALIZED = 0;
    var READYSTATE_LOADING = 1;
    var READYSTATE_LOADED = 2;
    var READYSTATE_INTERACTIVE = 3;
    var READYSTATE_COMPLETE = 4;

    function GetXmlHttpObject()
    {   
        var xmlHttpObj;
        try
        {
            // Firefox, Opera 8.0+, Safari
            xmlHttpObj=new XMLHttpRequest();
            return xmlHttpObj
        }
        catch (e)
        {
            // Internet Explorer
            try
            {
                xmlHttpObj=new ActiveXObject("Msxml2.XMLHTTP");
                return xmlHttpObj
            }
            catch (e)
            {
                try
                {
                    xmlHttpObj=new ActiveXObject("Microsoft.XMLHTTP");
                    return xmlHttpObj
                }
                catch (e)
                {
                    alert("Your browser does not support AJAX!");
                    return false;
                }
            }
        }
    }