'''Nothing there was removed''', but I don't know which you had, so here is where the close buttons can be configured. I have mine configured for one close button at the right end of the tabs bar. I also use "Ctrl+W" to close the active tab, or if I accidentally close it "Ctrl+Shift+T" to restore. "Ctrl+T" is same as new tab button. * http://kb.mozillazine.org/Browser.tabs.closeButtons '''Information on configuration variables''' available in [http://kb.mozillazine.org/About:config_entries about:config entries] and for users not familiar with the process there is [http://kb.mozillazine.org/About:config about:config] (How to change). You will find interesting reading on tabs in * '''Tabbed Browsing''' in Firefox<br>http://dmcritchie.mvps.org/firefox/tabs.htm * '''Tabs configuration''', extracted from About:config entries - MozillaZine Knowledge Base<br>http://dmcritchie.mvps.org/firefox/tabs_config.htm * 001 '''Tab Capacity Test'''<br>http://dmcritchie.mvps.org/firefox/tab_capacity/001_with_underscore.htm## * '''Tab Color Underscoring active/read/unread''' (Fx3.6) - Themes and Skins for Browser - userstyles.org<br>actually colors all borders not just an underline-- see picture in Tabs Bar Minimal Size<br>http://userstyles.org/styles/24728 * '''Tabs, Enlarge list-all-tabs button''' - Themes and Skins for Browser - userstyles.org<br>http://userstyles.org/styles/18553 * '''Tabs Bar Minimal Size''' - Themes and Skins for Browser - userstyles.org<br>http://userstyles.org/styles/9043 ---- You can make Firefox 4.0.1 and '''Firefox 5.0''' look like Firefox 3.6.17, see numbered items 1-10 in the following topic *[http://dmcritchie.mvps.org/firefox/firefox-problems.htm#fx4interface Fix Firefox 4.0 toolbar user interface, problems (Make Firefox 4.0 look like 3.6)]

I think the answer in in the first link of the first answer, but those options are spelled out in the following question: https://support.mozilla.com/questions/886703