You can open a list of all the cookies stored on your computer from the privacy settings window of firefox. If you look at the list after you have visited the website you should be able to see all the cookies that have been stored for that website and when each of them is due to expire. Obviously any that say they will expire "at end of session" should not be there when firefox is restarted. If you look at the list again after restarting firefox but before re-visiting the website you can check that all the cookies that were not due to expire are still present. (I have checked out the website and it does set some cookies with a 30 day expiry date, provided you have not configured firefox to delete cookies from that site at the end of the session.)

Hello imorro, except for cookies "not configured firefox to delete cookies from that site at the end of the session" as bug78 said correct above, also check in Preferences window > Privacy panel > History > Firefox will is set to Use custom settings for history > check Remember search and form history [v] and Accept cookies from sites[v], Keep until: they expire.

also see in Security panel > check Remember passwords for sites [v] if you enter a password in your card.

more : Settings for privacy, browsing history and do-not-track

thank you

History and cookies can be removed or not recorded several ways;

• 1) Running Firefox in Private Mode (nothing is recorded)
• 2) Privacy settings
  (Type about:preferences#privacy<enter> in the address bar.)
• 3) Many disk cleaners and anti-virus type programs can remove data from browsers. Open their settings and have them leave the browsers alone.
• 4) Mal-ware.