Each test below sets a cookie with some combination of the "max-age" or "expires" parameters. It turns out that Internet Explorer 6 (ie6), Internet Explorer 7 (ie7), and Internet Explorer 8 (ie8) do not support the "max-age" parameter (they just ignore it), but all browsers support the "expires" parameter as long as the date is formated in GMT time, e.g. "(new Date).toGMTString()".