No sweat,I missed it,too.
Glad you can check your email now.
Yes,when you set it to 1,to block third-party cookies,you will still probably get the occasional tracking cookie(s),though it should cut down on most of them.If you want to remove the tracking cookies,this shows how you can do that,plus keep the cookies you want.
http://kb.mozillazine.org/Cookies#Firefox_2
You can block doubleclick by going to Tools->Options->Privacy->Cookies->Exceptions,then typing doubleclick.net,then hitting Block.Then do the same thing again,but write doubleclick.com.