- Open a new tab and enter about:config.
- Enter in the search field browser.tabs.warnOnCloseOther.
- Now double click on the browser.tabs.warnOnCloseOther row to turn its value to false.
February 19, 2013
How to Get Rid of the Close Other Tabs Warning in Firefox
Starting with Firefox 16, they added a quite annoying warning dialog when you are trying to close other tabs. What is this? And even when you click on, do not warn me again, nothing happens. But there is a hack to get around it. But should it really be this hacky. Of course not. Any way this is how you fix it.