I tried to log on for advice on increasing my computer's security.
Using Firebug, I had discovered a one pixel "image" which caused my Mac to be studied by 2o7.net. I've since learned a bit more about tiny iframes and gifs doing this.
I checked with Firefox. The very first suggestion the gave was: "Don't accept 3rd party cookies." So, of course I turned off their acceptance.
Lo and behold, Stack Exchange requires enabling 3rd party cookies or else I can't log into my account?
It seems ironic.
Even if the reason is benign, wouldn't it be smart on such as site as this to include a word or two about why you need this 3rd-party cookie?