Increase Firefox Recently Closed Tabs Count

Firefox is currently the fastest growing Browser. It’s gaining popularity because of its much improved performance, reliability, and convenience to users. However, when you access its closed tab history, the application will only show the last 10 items.
By default, the Recently Closed Tabs can only show the last 10 closed tabs. You can always change this value to whatever you want, to 20 or 50 for instance.
Do this Steps:
(i) Type “about:config”In addressbar and press enter
(ii) It will ask you to confirm your action. Click I’ll be careful, I promise! to proceed.
(iii)Input or paste “browser.sessionstore.max_tabs_undo” in the Filter text box and hit Enter.
(iv)Now Your Filter displayed one result.
(v) Double click on it
(vi)Enter the number of tabs you want to be shown on the Recently Closed Tabs section and press OK.(exaample 20 or 30 )
(vi) close this tab.
The change will take effect immediately. You don’t have to close or restart Firefox.
Let’s see the result. First, click the History menu and press Recently closed Tabs now Firefox can show 20 tabs.

Enjoy........