function CreateHttpRequest()
{
    if(window.ActiveXObject)
    {
        try
        {
            return new ActiveXObject("Msxml2.XMLHTTP");
        }
        catch(exception1)
        {
            try
            {
                return new ActiveXObject("Microsoft.XMLHTTP");
            }
            catch(exception2)
            {
                return null;
            }
        }
    }
    else if(window.XMLHttpRequest)
    {
        return new XMLHttpRequest();
    }
    else
    {
        return null;
    }
}