Which language version of Firefox are you using? I'm going to guess that your card is the same as what my version calls a tab. Normally, if you have closed a tab, you will see "Undo Close Tab" on that right-click menu to re-open the last tab you closed. You also can find closed tabs on Firefox's History menu. Do you see anything listed there? Firefox's History menu also will list any recently closed windows that you can re-open. The tab list is per-window, so if the tab was in a different window, you need to open that first. If Firefox has simply stopped remembering tabs, please check these settings: (1) In a new tab, type or paste '''about:config''' in the address bar and press Enter. Click the button promising to be careful. (2) In the search box above the list, type or paste '''sess''' and pause while the list is filtered (3) These values might need to be adjusted: (A) '''browser.sessionstore.max_tabs_undo''': default value is 10, so up to 10 tabs per window can be re-opened; setting this to zero could cause the problem you're having (B) '''browser.sessionstore.max_windows_undo''': default value is 3, so up to 3 closed windows can be re-opened (There are many other session-related preferences. Please ask if you have a question about any of those.)