记得以前用Firefox 3.0.x时把Tools -> Options -> Tabs -> Always show the tab bar勾上就行了,升级到3.5以后就没用了,搜了下Knowledge Base,最后在

https://support.mozilla.com/tiki-view_forum_thread.php?locale=zh-CN&comments_parentId=184680&forumId=1

看到只要将about:config页中的browser.tabs.closeWindowWithLastTab项设为false即可