Why does a 2nd Firefox open when I click on a pinned tab?
90% of the time, when I click on one of the 10 pinned tabs to open it, a 2nd Firefox window opens up with the tab I clicked on, thus removing it from the original Firefox page (now only 9 pinned tabs). In other words, I have to minimize the 2nd window with the one tab and move it back to the original Firefox page (which then closes out the 2nd window). This is VERY VERY annoying~!
Wšě wotmołwy (1)
Make sure that you do not drag a tab slightly down in the browser window while clicking.
Current Firefox versions have a feature called tear-off tabs.
You can detach a tab from the current window and open it in a new window by dragging a tab in the browser window.
You can drag that tab back to the tab bar in the original window to undo that detaching.
bug489729 (Disable detach and tear off tab):