deleted file mode 100644
--- a/toolkit/locales/en-US/chrome/mozapps/extensions/about.dtd
+++ /dev/null
@@ -1,9 +0,0 @@
-<!-- This Source Code Form is subject to the terms of the Mozilla Public
-   - License, v. 2.0. If a copy of the MPL was not distributed with this
-   - file, You can obtain one at http://mozilla.org/MPL/2.0/. -->
-
-<!ENTITY  creator.label               "Created By:">
-<!ENTITY  developers.label            "Developers:">
-<!ENTITY  translators.label           "Translators:">
-<!ENTITY  contributors.label          "Contributors:">
-<!ENTITY  homepage.label              "Visit Home Page">

--- a/toolkit/locales/en-US/chrome/mozapps/extensions/extensions.dtd
+++ b/toolkit/locales/en-US/chrome/mozapps/extensions/extensions.dtd
@@ -75,18 +75,16 @@
 <!ENTITY cmd.showDetails.label                "Show More Information">
 <!ENTITY cmd.showDetails.accesskey            "S">
 <!ENTITY cmd.findUpdates.label                "Find Updates">
 <!ENTITY cmd.findUpdates.accesskey            "F">
 <!ENTITY cmd.preferencesWin.label             "Options">
 <!ENTITY cmd.preferencesWin.accesskey         "O">
 <!ENTITY cmd.preferencesUnix.label            "Preferences">
 <!ENTITY cmd.preferencesUnix.accesskey        "P">
-<!ENTITY cmd.about.label                      "About">
-<!ENTITY cmd.about.accesskey                  "A">
 
 <!ENTITY cmd.enableAddon.label                "Enable">
 <!ENTITY cmd.enableAddon.accesskey            "E">
 <!ENTITY cmd.disableAddon.label               "Disable">
 <!ENTITY cmd.disableAddon.accesskey           "D">
 <!ENTITY cmd.enableTheme.label                "Wear Theme">
 <!ENTITY cmd.enableTheme.accesskey            "W">
 <!ENTITY cmd.disableTheme.label               "Stop Wearing Theme">

--- a/toolkit/locales/en-US/chrome/mozapps/extensions/extensions.properties
+++ b/toolkit/locales/en-US/chrome/mozapps/extensions/extensions.properties
@@ -1,20 +1,12 @@
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
-#LOCALIZATION NOTE (aboutWindowTitle) %S is the addon name
-aboutWindowTitle=About %S
-aboutWindowCloseButton=Close
-#LOCALIZATION NOTE (aboutWindowVersionString) %S is the addon version
-aboutWindowVersionString=version %S
-#LOCALIZATION NOTE (aboutAddon) %S is the addon name
-aboutAddon=About %S
-
 #LOCALIZATION NOTE (uninstallNotice) %S is the add-on name
 uninstallNotice=%S has been removed.
 
 #LOCALIZATION NOTE (numReviews): Semicolon-separated list of plural forms.
 # See: http://developer.mozilla.org/en/docs/Localization_and_Plurals
 # #1 is the number of reviews
 numReviews=#1 review;#1 reviews
 

--- a/toolkit/locales/jar.mn
+++ b/toolkit/locales/jar.mn
@@ -91,17 +91,16 @@
   locale/@AB_CD@/mozapps/downloads/unknownContentType.properties  (%chrome/mozapps/downloads/unknownContentType.properties)
   locale/@AB_CD@/mozapps/downloads/unknownContentType.dtd         (%chrome/mozapps/downloads/unknownContentType.dtd)
   locale/@AB_CD@/mozapps/downloads/settingsChange.dtd             (%chrome/mozapps/downloads/settingsChange.dtd)
   locale/@AB_CD@/mozapps/downloads/downloads.properties           (%chrome/mozapps/downloads/downloads.properties)
   locale/@AB_CD@/mozapps/extensions/extensions.dtd                (%chrome/mozapps/extensions/extensions.dtd)
 #ifndef MOZ_FENNEC
   locale/@AB_CD@/mozapps/extensions/extensions.properties         (%chrome/mozapps/extensions/extensions.properties)
   locale/@AB_CD@/mozapps/extensions/blocklist.dtd                 (%chrome/mozapps/extensions/blocklist.dtd)
-  locale/@AB_CD@/mozapps/extensions/about.dtd                     (%chrome/mozapps/extensions/about.dtd)
   locale/@AB_CD@/mozapps/extensions/update.properties             (%chrome/mozapps/extensions/update.properties)
   locale/@AB_CD@/mozapps/extensions/newaddon.dtd                  (%chrome/mozapps/extensions/newaddon.dtd)
   locale/@AB_CD@/mozapps/extensions/newaddon.properties           (%chrome/mozapps/extensions/newaddon.properties)
 #endif
   locale/@AB_CD@/mozapps/handling/handling.dtd                    (%chrome/mozapps/handling/handling.dtd)
   locale/@AB_CD@/mozapps/handling/handling.properties             (%chrome/mozapps/handling/handling.properties)
   locale/@AB_CD@/mozapps/preferences/changemp.dtd                 (%chrome/mozapps/preferences/changemp.dtd)
   locale/@AB_CD@/mozapps/preferences/removemp.dtd                 (%chrome/mozapps/preferences/removemp.dtd)

deleted file mode 100644
--- a/toolkit/mozapps/extensions/content/about.js
+++ /dev/null
@@ -1,104 +0,0 @@
-// -*- indent-tabs-mode: nil; js-indent-level: 2 -*-
-
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-"use strict";
-
-/* import-globals-from ../../../content/contentAreaUtils.js */
-
-/* exported init, loadHomepage */
-
-ChromeUtils.import("resource://gre/modules/AddonManager.jsm");
-
-function init() {
-  var addon = window.arguments[0];
-  var extensionsStrings = document.getElementById("extensionsStrings");
-
-  document.documentElement.setAttribute("addontype", addon.type);
-
-  var iconURL = AddonManager.getPreferredIconURL(addon, 48, window);
-  if (iconURL) {
-    var extensionIcon = document.getElementById("extensionIcon");
-    extensionIcon.src = iconURL;
-  }
-
-  document.title = extensionsStrings.getFormattedString("aboutWindowTitle", [addon.name]);
-  var extensionName = document.getElementById("extensionName");
-  extensionName.textContent = addon.name;
-
-  var extensionVersion = document.getElementById("extensionVersion");
-  if (addon.version)
-    extensionVersion.setAttribute("value", extensionsStrings.getFormattedString("aboutWindowVersionString", [addon.version]));
-  else
-    extensionVersion.hidden = true;
-
-  var extensionDescription = document.getElementById("extensionDescription");
-  if (addon.description)
-    extensionDescription.textContent = addon.description;
-  else
-    extensionDescription.hidden = true;
-
-  var numDetails = 0;
-
-  var extensionCreator = document.getElementById("extensionCreator");
-  if (addon.creator) {
-    extensionCreator.setAttribute("value", addon.creator);
-    numDetails++;
-  } else {
-    extensionCreator.hidden = true;
-    var extensionCreatorLabel = document.getElementById("extensionCreatorLabel");
-    extensionCreatorLabel.hidden = true;
-  }
-
-  var extensionHomepage = document.getElementById("extensionHomepage");
-  var homepageURL = addon.homepageURL;
-  if (homepageURL) {
-    extensionHomepage.setAttribute("homepageURL", homepageURL);
-    extensionHomepage.setAttribute("tooltiptext", homepageURL);
-    numDetails++;
-  } else {
-    extensionHomepage.hidden = true;
-  }
-
-  numDetails += appendToList("extensionDevelopers", "developersBox", addon.developers);
-  numDetails += appendToList("extensionTranslators", "translatorsBox", addon.translators);
-  numDetails += appendToList("extensionContributors", "contributorsBox", addon.contributors);
-
-  if (numDetails == 0) {
-    var groove = document.getElementById("groove");
-    groove.hidden = true;
-    var extensionDetailsBox = document.getElementById("extensionDetailsBox");
-    extensionDetailsBox.hidden = true;
-  }
-
-  var acceptButton = document.documentElement.getButton("accept");
-  acceptButton.label = extensionsStrings.getString("aboutWindowCloseButton");
-
-  setTimeout(sizeToContent, 0);
-}
-
-function appendToList(aHeaderId, aNodeId, aItems) {
-  var header = document.getElementById(aHeaderId);
-  var node = document.getElementById(aNodeId);
-
-  if (!aItems || aItems.length == 0) {
-    header.hidden = true;
-    return 0;
-  }
-
-  for (let currentItem of aItems) {
-    var label = document.createElement("label");
-    label.textContent = currentItem;
-    label.setAttribute("class", "contributor");
-    node.appendChild(label);
-  }
-
-  return aItems.length;
-}
-
-function loadHomepage(aEvent) {
-  window.close();
-  openURL(aEvent.target.getAttribute("homepageURL"));
-}

deleted file mode 100644
--- a/toolkit/mozapps/extensions/content/about.xul
+++ /dev/null
@@ -1,57 +0,0 @@
-<?xml version="1.0"?>
-
-<!-- This Source Code Form is subject to the terms of the Mozilla Public
-   - License, v. 2.0. If a copy of the MPL was not distributed with this
-   - file, You can obtain one at http://mozilla.org/MPL/2.0/. -->
-
-<?xml-stylesheet href="chrome://global/skin/" type="text/css"?> 
-<?xml-stylesheet href="chrome://mozapps/skin/extensions/about.css" type="text/css"?> 
-
-<!DOCTYPE dialog SYSTEM "chrome://mozapps/locale/extensions/about.dtd">
-
-<dialog id="genericAbout"
-        xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"
-        onload="init();"
-        buttons="accept"
-        buttoniconaccept="close"
-        onaccept="close();">
-
-  <script type="application/javascript" src="chrome://mozapps/content/extensions/about.js"/>
-  <script type="application/javascript" src="chrome://global/content/contentAreaUtils.js"/>
-
-  <stringbundleset id="aboutSet">
-    <stringbundle id="extensionsStrings" src="chrome://mozapps/locale/extensions/extensions.properties"/>
-  </stringbundleset>
-
-  <vbox id="clientBox" flex="1">
-    <hbox class="basic-info">
-      <vbox pack="center">
-        <image id="extensionIcon"/>
-      </vbox>
-      <vbox flex="1">
-        <label id="extensionName"/>
-        <label id="extensionVersion" crop="end"/>
-      </vbox>
-    </hbox>
-    <description id="extensionDescription" class="boxIndent"/>
-
-    <separator id="groove" class="groove"/>
-
-    <vbox id="extensionDetailsBox" flex="1">
-      <label id="extensionCreatorLabel" class="sectionTitle">&creator.label;</label>
-      <hbox id="creatorBox" class="boxIndent">
-        <label id="extensionCreator" flex="1" crop="end"/>
-        <label id="extensionHomepage" onclick="if (event.button == 0) { loadHomepage(event); }"
-               class="text-link" value="&homepage.label;"/>
-      </hbox>
-  
-      <label id="extensionDevelopers" class="sectionTitle">&developers.label;</label>
-      <vbox flex="1" id="developersBox" class="boxIndent"/>
-      <label id="extensionTranslators" class="sectionTitle">&translators.label;</label>
-      <vbox flex="1" id="translatorsBox" class="boxIndent"/>
-      <label id="extensionContributors" class="sectionTitle">&contributors.label;</label>
-      <vbox flex="1" id="contributorsBox" class="boxIndent"/>
-    </vbox>
-  </vbox>
-
-</dialog>

--- a/toolkit/mozapps/extensions/content/extensions.js
+++ b/toolkit/mozapps/extensions/content/extensions.js
@@ -146,17 +146,16 @@ function initialize(event) {
     gDragDrop.onDragOver(event);
   });
   addonPage.addEventListener("drop", function(event) {
     gDragDrop.onDrop(event);
   });
   addonPage.addEventListener("keypress", function(event) {
     gHeader.onKeyPress(event);
   });
-
   if (!isDiscoverEnabled()) {
     gViewDefault = "addons://list/extension";
   }
 
   gViewController.initialize();
   gCategories.initialize();
   gHeader.initialize();
   gEventManager.initialize();
@@ -853,18 +852,19 @@ var gViewController = {
 
   loadViewInternal(aViewId, aPreviousView, aState) {
     var view = this.parseViewId(aViewId);
 
     if (!view.type || !(view.type in this.viewObjects))
       throw Components.Exception("Invalid view: " + view.type);
 
     var viewObj = this.viewObjects[view.type];
-    if (!viewObj.node)
+    if (!viewObj.node) {
       throw Components.Exception("Root node doesn't exist for '" + view.type + "' view");
+    }
 
     if (this.currentViewObj && aViewId != aPreviousView) {
       try {
         let canHide = this.currentViewObj.hide();
         if (canHide === false)
           return;
         this.displayedView.removeAttribute("loading");
       } catch (e) {
@@ -1160,31 +1160,16 @@ var gViewController = {
         if (hasInlineOptions(aAddon)) {
           gViewController.commands.cmd_showItemDetails.doCommand(aAddon, true);
         } else if (aAddon.optionsType == AddonManager.OPTIONS_TYPE_TAB) {
           openOptionsInTab(aAddon.optionsURL);
         }
       }
     },
 
-    cmd_showItemAbout: {
-      isEnabled(aAddon) {
-        // XXXunf This may be applicable to install items too. See bug 561260
-        return !!aAddon;
-      },
-      doCommand(aAddon) {
-        var aboutURL = aAddon.aboutURL;
-        if (aboutURL)
-          openDialog(aboutURL, "", "chrome,centerscreen,modal", aAddon);
-        else
-          openDialog("chrome://mozapps/content/extensions/about.xul",
-                     "", "chrome,centerscreen,modal", aAddon);
-      }
-    },
-
     cmd_enableItem: {
       isEnabled(aAddon) {
         if (!aAddon)
           return false;
         let addonType = AddonManager.addonTypes[aAddon.type];
         return (!(addonType.flags & AddonManager.TYPE_SUPPORTS_ASK_TO_ACTIVATE) &&
                 hasPermission(aAddon, "enable"));
       },
@@ -1773,16 +1758,20 @@ var gCategories = {
     this.node.value = gViewDefault;
     this.node.value = Services.prefs.getStringPref(PREF_UI_LASTCATEGORY, "");
 
     // If there was no last view or no existing category matched the last view
     // then switch to the default category
     if (!this.node.selectedItem) {
       this.node.value = gViewDefault;
     }
+    // If the previous node is the discover panel which has since been disabled set to default
+    if (this.node.value == "addons://discover/" && !isDiscoverEnabled()) {
+      this.node.value = gViewDefault;
+    }
 
     this.node.addEventListener("select", () => {
       gViewController.loadView(this.node.selectedItem.value);
     });
 
     this.node.addEventListener("click", (aEvent) => {
       var selectedItem = this.node.selectedItem;
       if (aEvent.target.localName == "richlistitem" &&

--- a/toolkit/mozapps/extensions/content/extensions.xul
+++ b/toolkit/mozapps/extensions/content/extensions.xul
@@ -59,19 +59,16 @@
                 accesskey="&cmd.preferencesWin.accesskey;"/>
 #else
                 label="&cmd.preferencesUnix.label;"
                 accesskey="&cmd.preferencesUnix.accesskey;"/>
 #endif
       <menuitem id="menuitem_findUpdates" command="cmd_findItemUpdates"
                 label="&cmd.findUpdates.label;"
                 accesskey="&cmd.findUpdates.accesskey;"/>
-      <menuitem id="menuitem_about" command="cmd_showItemAbout"
-                label="&cmd.about.label;"
-                accesskey="&cmd.about.accesskey;"/>
     </menupopup>
 
     <menulist popuponly="true" id="ContentSelectDropdown" hidden="true">
       <menupopup rolluponmousewheel="true"
                  activateontab="true" position="after_start"
                  level="parent"
 #ifdef XP_WIN
                  consumeoutsideclicks="false" ignorekeys="shortcuts"
@@ -114,17 +111,16 @@
   </commandset>
 
   <!-- view commands - these act on the selected addon -->
   <commandset id="viewCommandSet"
               events="richlistbox-select" commandupdater="true">
     <command id="cmd_showItemDetails"/>
     <command id="cmd_findItemUpdates"/>
     <command id="cmd_showItemPreferences"/>
-    <command id="cmd_showItemAbout"/>
     <command id="cmd_enableItem"/>
     <command id="cmd_disableItem"/>
     <command id="cmd_installItem"/>
     <command id="cmd_uninstallItem"/>
     <command id="cmd_cancelUninstallItem"/>
     <command id="cmd_cancelOperation"/>
     <command id="cmd_contribute"/>
     <command id="cmd_askToActivateItem"/>

--- a/toolkit/mozapps/extensions/jar.mn
+++ b/toolkit/mozapps/extensions/jar.mn
@@ -5,18 +5,16 @@
 toolkit.jar:
 #ifndef MOZ_FENNEC
 % content mozapps %content/mozapps/
 * content/mozapps/extensions/extensions.xul                     (content/extensions.xul)
   content/mozapps/extensions/extensions.css                     (content/extensions.css)
   content/mozapps/extensions/extensions.js                      (content/extensions.js)
 * content/mozapps/extensions/extensions.xml                     (content/extensions.xml)
   content/mozapps/extensions/updateinfo.xsl                     (content/updateinfo.xsl)
-  content/mozapps/extensions/about.xul                          (content/about.xul)
-  content/mozapps/extensions/about.js                           (content/about.js)
   content/mozapps/extensions/blocklist.xul                      (content/blocklist.xul)
   content/mozapps/extensions/blocklist.js                       (content/blocklist.js)
   content/mozapps/extensions/blocklist.css                      (content/blocklist.css)
   content/mozapps/extensions/blocklist.xml                      (content/blocklist.xml)
   content/mozapps/extensions/update.html                        (content/update.html)
   content/mozapps/extensions/update.js                          (content/update.js)
   content/mozapps/extensions/update.css                         (content/update.css)
   content/mozapps/extensions/eula.xul                           (content/eula.xul)

deleted file mode 100644
--- a/toolkit/mozapps/extensions/test/browser/addon_about.xul
+++ /dev/null
@@ -1,6 +0,0 @@
-<?xml version="1.0"?>
-<?xml-stylesheet href="chrome://global/skin/" type="text/css"?>
-<window xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"
-        id="addon-test-about-window">
-  <label value="Oh hai!"/>
-</window>

--- a/toolkit/mozapps/extensions/test/browser/browser.ini
+++ b/toolkit/mozapps/extensions/test/browser/browser.ini
@@ -1,13 +1,12 @@
 [DEFAULT]
 tags = addons
 support-files =
   addons/*
-  addon_about.xul
   addon_prefs.xul
   discovery.html
   head.js
   more_options.xul
   options.xul
   plugin_test.html
   redirect.sjs
   releaseNotes.xhtml
@@ -27,18 +26,16 @@ support-files =
   !/toolkit/mozapps/extensions/test/xpinstall/theme.xpi
   !/toolkit/mozapps/extensions/test/xpinstall/unsigned.xpi
   !/toolkit/mozapps/extensions/test/xpinstall/amosigned.xpi
   !/toolkit/mozapps/extensions/test/xpinstall/amosigned-restart-required.xpi
 
 [browser_CTP_plugins.js]
 tags = blocklist
 skip-if = buildapp == 'mulet'
-[browser_about.js]
-skip-if = os == 'linux' || os == 'win' # bug 632290
 [browser_bug523784.js]
 [browser_bug562797.js]
 [browser_bug562854.js]
 [browser_bug562890.js]
 skip-if = os == 'win' && !debug # Disabled on Windows opt/PGO builds due to intermittent failures (bug 1135866)
 [browser_bug562899.js]
 skip-if = buildapp == 'mulet'
 [browser_bug562992.js]

deleted file mode 100644
--- a/toolkit/mozapps/extensions/test/browser/browser_about.js
+++ /dev/null
@@ -1,84 +0,0 @@
-/* Any copyright is dedicated to the Public Domain.
- * http://creativecommons.org/publicdomain/zero/1.0/
- */
-
-/**
- * Tests the default and custom "about" dialogs of add-ons.
- *
- * Test for bug 610661 <https://bugzilla.mozilla.org/show_bug.cgi?id=610661>:
- * Addon object not passed to custom about dialogs.
- */
-
-var gManagerWindow;
-
-const URI_ABOUT_DEFAULT = "chrome://mozapps/content/extensions/about.xul";
-const URI_ABOUT_CUSTOM = CHROMEROOT + "addon_about.xul";
-
-function test() {
-  requestLongerTimeout(2);
-
-  waitForExplicitFinish();
-
-  var gProvider = new MockProvider();
-  gProvider.createAddons([{
-    id: "test1@tests.mozilla.org",
-    name: "Test add-on 1",
-    description: "foo"
-  },
-  {
-    id: "test2@tests.mozilla.org",
-    name: "Test add-on 2",
-    description: "bar",
-    aboutURL: URI_ABOUT_CUSTOM
-  }]);
-
-  open_manager("addons://list/extension", function(aManager) {
-    gManagerWindow = aManager;
-
-    test_about_window("Test add-on 1", URI_ABOUT_DEFAULT, function() {
-      test_about_window("Test add-on 2", URI_ABOUT_CUSTOM, function() {
-        close_manager(gManagerWindow, finish);
-      });
-    });
-  });
-}
-
-function test_about_window(aAddonItemName, aExpectedAboutUri, aCallback) {
-  var addonList = gManagerWindow.document.getElementById("addon-list");
-  for (var addonItem of addonList.childNodes) {
-    if (addonItem.hasAttribute("name") &&
-        addonItem.getAttribute("name") === aAddonItemName)
-      break;
-  }
-
-  info("Waiting for about dialog");
-  Services.ww.registerNotification(function TEST_ww_observer(aSubject, aTopic,
-                                                             aData) {
-    if (aTopic == "domwindowclosed") {
-      Services.ww.unregisterNotification(TEST_ww_observer);
-
-      info("About dialog closed, waiting for focus on browser window");
-      waitForFocus(() => executeSoon(aCallback));
-    } else if (aTopic == "domwindowopened") {
-      info("About dialog opened, waiting for focus");
-
-      let win = aSubject.QueryInterface(Ci.nsIDOMEventTarget);
-      waitForFocus(function() {
-        info("Saw about dialog");
-
-        is(win.location,
-           aExpectedAboutUri,
-           "The correct add-on about window should have opened");
-
-        is(win.arguments && win.arguments[0] && win.arguments[0].name,
-           aAddonItemName,
-           "window.arguments[0] should refer to the add-on object");
-
-        executeSoon(() => win.close());
-      }, win);
-    }
-  });
-
-  gManagerWindow.gViewController.doCommand("cmd_showItemAbout",
-                                           addonItem.mAddon);
-}

--- a/toolkit/mozapps/extensions/test/browser/browser_discovery.js
+++ b/toolkit/mozapps/extensions/test/browser/browser_discovery.js
@@ -510,17 +510,17 @@ add_test(function() {
     // This will actually stop the about:blank load
     browser.stop();
   });
 });
 
 // Test for Bug 703929 - Loading the discover view from a chrome XUL file fails when
 // the add-on manager is reopened.
 add_test(function() {
-  const url = "chrome://mochitests/content/" + RELATIVE_DIR + "addon_about.xul";
+  const url = "chrome://mochitests/content/" + RELATIVE_DIR + "addon_prefs.xul";
   Services.prefs.setCharPref(PREF_DISCOVERURL, url);
 
   open_manager("addons://discover/", function(aWindow) {
     gManagerWindow = aWindow;
     gCategoryUtilities = new CategoryUtilities(gManagerWindow);
 
     var browser = gManagerWindow.document.getElementById("discover-browser");
     is(getURL(browser), url, "Loading a chrome XUL file should work");

deleted file mode 100644
--- a/toolkit/themes/osx/mozapps/extensions/about.css
+++ /dev/null
@@ -1,78 +0,0 @@
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-#genericAbout {
-  padding: 0px;
-  min-height: 200px;
-  max-height: 400px;
-  width: 30em;
-}
-
-#clientBox {
-  background-color: -moz-Dialog;
-  color: -moz-DialogText;
-}
-
-.basic-info {
-  padding: 10px;
-}
-
-#extensionIcon {
-  list-style-image: url("chrome://mozapps/skin/extensions/extensionGeneric.svg");
-  max-width: 64px;
-  max-height: 64px;
-  margin-inline-end: 6px;
-}
-
-#genericAbout[addontype="theme"] #extensionIcon {
-  list-style-image: url("chrome://mozapps/skin/extensions/themeGeneric.svg");
-}
-
-#genericAbout[addontype="locale"] #extensionIcon {
-  list-style-image: url("chrome://mozapps/skin/extensions/localeGeneric.svg");
-}
-
-#genericAbout[addontype="plugin"] #extensionIcon {
-  list-style-image: url("chrome://mozapps/skin/plugins/pluginGeneric.svg");
-}
-
-#genericAbout[addontype="dictionary"] #extensionIcon {
-  list-style-image: url("chrome://mozapps/skin/extensions/dictionaryGeneric.svg");
-}
-
-#extensionName {
-  font-size: 200%;
-  font-weight: bolder;
-}
-
-#extensionVersion {
-  font-weight: bold;
-}
-
-#extensionDescription {
-  margin-top: 4px;
-}
-
-#groove {
-  margin-top: 8px;
-}
-
-#extensionDetailsBox {
-  overflow: auto;
-  min-height: 100px;
-}
-
-.boxIndent {
-  margin-inline-start: 18px;
-}
-
-#extensionCreator, .contributor {
-  margin: 0px;
-} 
-
-.sectionTitle {
-  padding: 2px 0px 3px 0px;
-  margin-top: 3px;
-  font-weight: bold;
-}

--- a/toolkit/themes/osx/mozapps/jar.mn
+++ b/toolkit/themes/osx/mozapps/jar.mn
@@ -7,17 +7,16 @@ toolkit.jar:
   skin/classic/mozapps/downloads/buttons.png                      (downloads/buttons.png)
   skin/classic/mozapps/downloads/unknownContentType.css           (downloads/unknownContentType.css)
   skin/classic/mozapps/extensions/discover-logo.png               (extensions/discover-logo.png)
   skin/classic/mozapps/extensions/rating-won.png                  (extensions/rating-won.png)
   skin/classic/mozapps/extensions/rating-not-won.png              (extensions/rating-not-won.png)
   skin/classic/mozapps/extensions/cancel.png                      (extensions/cancel.png)
   skin/classic/mozapps/extensions/toolbarbutton-dropmarker.png    (extensions/toolbarbutton-dropmarker.png)
   skin/classic/mozapps/extensions/heart.png                       (extensions/heart.png)
-  skin/classic/mozapps/extensions/about.css                       (extensions/about.css)
 * skin/classic/mozapps/extensions/extensions.css                  (extensions/extensions.css)
   skin/classic/mozapps/extensions/eula.css                        (extensions/eula.css)
   skin/classic/mozapps/extensions/blocklist.css                   (extensions/blocklist.css)
 * skin/classic/mozapps/extensions/newaddon.css                    (extensions/newaddon.css)
   skin/classic/mozapps/plugins/pluginHelp-16.png                  (plugins/pluginHelp-16.png)
   skin/classic/mozapps/profile/profileicon.png                    (profile/profileicon.png)
   skin/classic/mozapps/profile/profileSelection.css               (profile/profileSelection.css)
   skin/classic/mozapps/profile/profileicon-selected.png           (profile/profileicon-selected.png)
@@ -25,9 +24,9 @@ toolkit.jar:
 * skin/classic/mozapps/update/updates.css                         (update/updates.css)
   skin/classic/mozapps/xpinstall/xpinstallConfirm.css             (extensions/xpinstallConfirm.css)
   skin/classic/mozapps/handling/handling.css                      (handling/handling.css)
 
 #if MOZ_BUILD_APP == browser
 [browser/extensions/{972ce4c6-7e08-4474-a285-3208198ce6fd}] chrome.jar:
 #elif MOZ_SEPARATE_MANIFEST_FOR_THEME_OVERRIDES
 [extensions/{972ce4c6-7e08-4474-a285-3208198ce6fd}] chrome.jar:
-#endif
\ No newline at end of file
+#endif

--- a/toolkit/themes/shared/non-mac.jar.inc.mn
+++ b/toolkit/themes/shared/non-mac.jar.inc.mn
@@ -36,17 +36,16 @@
   skin/classic/global/tree/columnpicker.gif                (../../windows/global/tree/columnpicker.gif)
   skin/classic/global/tree/sort-asc.png                    (../../windows/global/tree/sort-asc.png)
   skin/classic/global/tree/sort-dsc.png                    (../../windows/global/tree/sort-dsc.png)
   skin/classic/global/tree/sort-asc-classic.png            (../../windows/global/tree/sort-asc-classic.png)
   skin/classic/global/tree/sort-dsc-classic.png            (../../windows/global/tree/sort-dsc-classic.png)
 
   skin/classic/mozapps/downloads/downloadButtons.png         (../../windows/mozapps/downloads/downloadButtons.png)
   skin/classic/mozapps/downloads/unknownContentType.css      (../../windows/mozapps/downloads/unknownContentType.css)
-  skin/classic/mozapps/extensions/about.css                  (../../windows/mozapps/extensions/about.css)
   skin/classic/mozapps/extensions/blocklist.css              (../../windows/mozapps/extensions/blocklist.css)
   skin/classic/mozapps/extensions/discover-logo.png          (../../windows/mozapps/extensions/discover-logo.png)
   skin/classic/mozapps/extensions/rating-won.png             (../../windows/mozapps/extensions/rating-won.png)
   skin/classic/mozapps/extensions/rating-not-won.png         (../../windows/mozapps/extensions/rating-not-won.png)
   skin/classic/mozapps/extensions/cancel.png                 (../../windows/mozapps/extensions/cancel.png)
   skin/classic/mozapps/extensions/eula.css                   (../../windows/mozapps/extensions/eula.css)
   skin/classic/mozapps/handling/handling.css                 (../../windows/mozapps/handling/handling.css)
   skin/classic/mozapps/plugins/pluginHelp-16.png             (../../windows/mozapps/plugins/pluginHelp-16.png)

deleted file mode 100644
--- a/toolkit/themes/windows/mozapps/extensions/about.css
+++ /dev/null
@@ -1,91 +0,0 @@
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-#genericAbout {
-  padding: 0px;
-  min-height: 200px;
-  max-height: 400px;
-  width: 30em;
-}
-
-#clientBox {
-  background-color: -moz-Dialog;
-  color: -moz-DialogText;
-}
-
-@media (-moz-windows-compositor) {
-  #genericAbout {
-    -moz-appearance: -moz-win-glass;
-    background: transparent;
-  }
-
-  #clientBox {
-    -moz-appearance: -moz-win-exclude-glass;
-  }
-}
-
-
-.basic-info {
-  padding: 10px;
-}
-
-#extensionIcon {
-  list-style-image: url("chrome://mozapps/skin/extensions/extensionGeneric.svg");
-  max-width: 64px;
-  max-height: 64px;
-  margin-inline-end: 6px;
-}
-
-#genericAbout[addontype="theme"] #extensionIcon {
-  list-style-image: url("chrome://mozapps/skin/extensions/themeGeneric.svg");
-}
-
-#genericAbout[addontype="locale"] #extensionIcon {
-  list-style-image: url("chrome://mozapps/skin/extensions/localeGeneric.svg");
-}
-
-#genericAbout[addontype="plugin"] #extensionIcon {
-  list-style-image: url("chrome://mozapps/skin/plugins/pluginGeneric.svg");
-}
-
-#genericAbout[addontype="dictionary"] #extensionIcon {
-  list-style-image: url("chrome://mozapps/skin/extensions/dictionaryGeneric.svg");
-}
-
-#extensionName {
-  font-size: 200%;
-  font-weight: bolder;
-}
-
-#extensionVersion {
-  font-weight: bold;
-}
-
-#extensionDescription {
-  margin-top: 4px;
-}
-
-#groove {
-  margin-top: 8px;
-}
-
-#extensionDetailsBox {
-  overflow: auto;
-  min-height: 100px;
-}
-
-.boxIndent {
-  margin-inline-start: 18px;
-}
-
-#extensionCreator, .contributor {
-  margin: 0px;
-} 
-
-.sectionTitle {
-  padding: 2px 0px 3px 0px;
-  margin-top: 3px;
-  font-weight: bold;
-}
-