User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; fr-FR; rv:1.7.10) Gecko/20050716 Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.1; fr-FR; rv:1.7.10) Gecko/20050716 In preferences> navigator> tabs, there is an option "mask tab bar if only one open". If this is UNCHECKED, one would expect that the tab bar remains open. However, this setting is ignored if one accidentally closes the last tab. Reproducible: Always Steps to Reproduce: 1. Under preferences> navigator> tabs: uncheck "mask tab bar if only one open". Select OK to save when exit preferences. 2. Press the left icon in the tab bar several times, to open several tabs. 3. Press the "X" at the right of the tab bar, until only one tab remains. Press the "X" one more time. Actual Results: The tab bar is defined by step 1. Numerous tabs are opened in step 2. The tabs are closed in step 3. When only one tab remains, pressing "X" removes the tab bar. Expected Results: When only one tab remains, pressing "X" should have no effect, if preferences> navigator> tabs> "mask tab bar if only one open" is UNCHECKED. (The default is - or was - checked.) Workaround = open menu "display> tool_bars", click "tab_bar" so the check mark reappears. It is more than a trivial problem for those who regularly use tabs. Effectively, the preference setting for "mask tab bar if only one open" is ignored. (And assumed to be checked.) Occurs with both classic and modern themes, present for a long time.
Related to Core bug 150099?
Yes, see bug 150099 comment 19. That was by design. But you are not the only one who does not prefer this. *** This bug has been marked as a duplicate of 156082 ***