on Firefox window there is a option of history & in history there is a option of recently closed tabs in which it shows the tabs which i closed most lastly. and now i wanted to know how to delete this memory.
-> go to Tools Menu -> Clear Recent History -> Time range to clear: select "EVERYTHING" -> click Details (small arrow) button -> place Checkmarks on Browsing and Download History -> click Clear Now
If you want Firefox to automatically Clear your Browsing history when you close Firefox, do this:
-> go to Tools Menu -> Options -> Privacy -> History section -> Firefox will: select "Use Custom Settings for History" -> REMOVE Checkmark from "Permanent Private Browsing mode" -> place CHECKMARKS on:
1) Remember my Browsing History 2) Remember Download History 3) Remember Search History 4) Accept Cookies from sites -> select "Exceptions..." button -> Click "Remove All Sites" at the bottom of "Exception - Cookies" window
4a) Accept Third-party Cookies -> under "Keep Until" select "They Expire"
-> place CHECKMARK on CLEAR HISTORY WHEN FIREFOX CLOSES -> click Settings... button -> place Checkmarks on the Options you do not want Firefox to remember -> click OK
To open the about:config page, type about:config in the location (address) bar and press the "Enter" key, just like you type the url of a website to open a website.
If you see a warning then you can confirm that you want to access that page.
Use the Filter bar at to top of the about:config page to locate a preference more easily.
Preferences that have been modified show as bold(user set).
Preferences can be reset to the default or changed via the right-click context menu.
I know all of the previous advice but I don’t want to have to clear everything or quit Firefox to get rid of the recently closed tabs. I want disable this feature permanently as I feel that it is a major security risk.
If you do not want to be able to reopen closed tabs then you can set the browser.sessionstore.max_tabs_undo pref to 0 on the about:config page.
This won't work for closed windows because Firefox always keeps at least one closed window in the recently closed windows list if the browser.sessionstore.max_windows_undo pref is set to 0.