A hidden preference has been added to Firefox 18 which allows user to turn off annoying Close Other Tabs prompt shown by the browser. In Firefox, we can close all other tabs except the active tab we’re facing by right-clicking on tab bar and selecting “Close Other Tabs” menu item. But here Firefox prompts you with Confirm close dialog with options: Close tabs and Cancel to stop closing the tabs. Users feel this dialog as redundant as they’ve already turned off “warn me when closing multiple tabs“option, they’ve gut feeling they shouldn’t get this.
Disabling Close Other Tabs warning dialog
Due to more users requests Mozilla has landed a hidden Preference browser.tabs.warnOnCloseOtherTabs in Firefox 18 Aurora and Nightly channels. If you don’t want to interrupted by Confirm close prompt dialog when close other tabs is selected you need to turn above preference value to “false” in about:config.
For current and earlier Firefox versions you can achieve this by using Tab Mix Plus add-on. Mozilla plans to also add this preference to Firefox 17 Beta with the next update.