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