diff --git a/Makefile b/Makefile
index 3d8f39d..87538fb 100644
--- a/Makefile
+++ b/Makefile
@@ -2,12 +2,13 @@
 # SPDX-License-Identifier: GPL-3.0-or-later
 
 USERCHROME_FILES := $(sort $(wildcard src/userChrome/*.css))
+USERCONTENT_FILES := $(sort $(wildcard src/userContent/*.css))
 HOMEPAGE_FILES := head.html distro_links.html bottom.html
 DISTRO := postmarketOS
 DESTDIR :=
 FIREFOX_DIR := /usr/lib/firefox
 
-all: out/home.html out/userChrome.css
+all: out/home.html out/userChrome.css out/userContent.css
 
 clean:
 	rm -rf out
@@ -22,6 +23,9 @@ out/home.html: src/homepage/*.html out
 out/userChrome.css: $(USERCHROME_FILES) out
 	cat $(USERCHROME_FILES) > $@
 
+out/userContent.css: $(USERCONTENT_FILES) out
+	cat $(USERCONTENT_FILES) > $@
+
 install: all
 	install -Dm644 src/policies.json \
 		"$(DESTDIR)/etc/firefox/policies/policies.json"
@@ -33,5 +37,7 @@ install: all
 		"$(DESTDIR)/usr/share/mobile-config-firefox/home.html"
 	install -Dm644 "out/userChrome.css" \
 		"$(DESTDIR)/etc/mobile-config-firefox/userChrome.css"
+	install -Dm644 "out/userContent.css" \
+		"$(DESTDIR)/etc/mobile-config-firefox/userContent.css"
 
 .PHONY: all clean install
diff --git a/src/mobile-config-autoconfig.js b/src/mobile-config-autoconfig.js
index 07e3194..ae2ef70 100644
--- a/src/mobile-config-autoconfig.js
+++ b/src/mobile-config-autoconfig.js
@@ -31,3 +31,19 @@ if (chromeFile.exists() && defaultChrome.exists() &&
 if (!chromeFile.exists()) {
   defaultChrome.copyTo(chromeDir, "userChrome.css");
 }
+
+// Create nsIFile objects for userContent.css in <profile>/chrome/ and in /etc/
+var contentFile = chromeDir.clone();
+contentFile.append("userContent.css");
+var defaultContent = new FileUtils.File("/etc/mobile-config-firefox/userContent.css");
+
+// Remove the existing userContent.css if older than the installed one
+if (contentFile.exists() && defaultContent.exists() &&
+    contentFile.lastModifiedTime < defaultContent.lastModifiedTime) {
+  contentFile.remove(false);
+}
+
+// Copy userContent.css to <profile>/chrome/
+if (!contentFile.exists()) {
+  defaultContent.copyTo(chromeDir, "userContent.css");
+}
diff --git a/src/userContent/preferences.css b/src/userContent/preferences.css
new file mode 100644
index 0000000..66ff115
--- /dev/null
+++ b/src/userContent/preferences.css
@@ -0,0 +1,17 @@
+@-moz-document url("about:preferences"), url-prefix("about:preferences") {
+    /* avoid that sidebar is too wide */
+    .navigation {
+        max-width: 50px;
+    }
+
+    /* reduce space around category icons */
+    #categories > .category {
+        margin-inline-start: 2px !important;
+        padding-inline: 2px !important;
+    }
+
+    /* reduce space around footer icons (addons, help) */
+    .sidebar-footer-list {
+        margin-inline: 2px !important;
+    }
+}