Here I document all the customizations I do to my Firefox profile (now focused at the version 5.0). The goal is to maximize the screen size used for content, and that means the UI must be minimal. The status bar, bookmark toolbar and menubar are hidden, the search bar too, and some extensions are added to help with this configuration. This is the end result, for now.

Extensions compatible or hacked to work with Firefox 5.0:

• http://getfirebug.com/
• https://addons.mozilla.org/en-US/firefox/addon/433/
• https://addons.mozilla.org/en-US/firefox/addon/new-tab-jumpstart/
• http://github.com/gdamjan/eznav (forked/hacked)

Needed extensions:

• Mail notifier

Some settings that I configure in about:config (stored in prefs.js in the profile):

// go to normal google search on random text in the location bar 
// .. instead of „I feel lucky“
user_pref("keyword.URL", "http://www.google.com/search?q=");

// these are configured from the preferences GUI, but still:
user_pref("general.smoothScroll", true);
user_pref("accessibility.typeaheadfind", true);
user_pref("accessibility.typeaheadfind.enablesound", false);
user_pref("dom.disable_window_move_resize", true);
user_pref("dom.event.contextmenu.enabled", false);

user_pref("browser.tabs.closeWindowWithLastTab", false);

// new tabs in background
user_pref("browser.tabs.loadBookmarksInBackground", true);
user_pref("browser.tabs.loadDivertedInBackground", true);

// backspace goes back in history
user_pref("browser.backspace_action", 0);
// don't load a new page on middle click (paste) inside the page
user_pref("middlemouse.contentLoadURL", false);
// better all tabs list
user_pref("browser.allTabs.previews", true);

Some additional UI customizations in chrome/userChrome.css:

/*
 * Do not remove the @namespace line -- it's required for correct functioning
 */
@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"); 
/* set default namespace to XUL */


menubar, menubutton, menulist, menu, menuitem, textbox, toolbar, tab,
tree, tooltip, statusbar, * {
  font: "DejaVu Sans" !important;
  font-size: 11px !important;
}

#urlbar * {
  font-family: monospace !important;
  font-size: 10px !important;
}

Also configured in the UI (and stored in localstore.rdf):

• hide the statusbar
• hide the bookmarks toolbar

<?xml version="1.0"?>
<RDF:RDF xmlns:NC="http://home.netscape.com/NC-rdf#"
         xmlns:RDF="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
...
  <RDF:Description RDF:about="chrome://browser/content/browser.xul#status-bar"
                   hidden="true" />
  <RDF:Description RDF:about="chrome://browser/content/browser.xul#PersonalToolbar"
                   collapsed="true"
                   currentset="personal-bookmarks" />
...
</RDF:RDF>