diff --git a/browser/components/preferences/in-content/content.xul b/browser/components/preferences/in-content/content.xul
index 0ea918651f4e..30857b205709 100644
--- a/browser/components/preferences/in-content/content.xul
+++ b/browser/components/preferences/in-content/content.xul
@@ -90,7 +90,7 @@
   <hbox align="center">
     <label control="defaultFont" accesskey="&defaultFont.accesskey;">&defaultFont.label;</label>
     <menulist id="defaultFont" flex="1"/>
-    <label control="defaultFontSize" accesskey="&defaultSize.accesskey;">&defaultSize.label;</label>
+    <label id="defaultFontSizeLabel" control="defaultFontSize" accesskey="&defaultSize.accesskey;">&defaultSize.label;</label>
     <menulist id="defaultFontSize">
       <menupopup>
         <menuitem value="9" label="9"/>
diff --git a/browser/themes/shared/incontentprefs/preferences.inc.css b/browser/themes/shared/incontentprefs/preferences.inc.css
index 84a046e7cf29..054362b80019 100644
--- a/browser/themes/shared/incontentprefs/preferences.inc.css
+++ b/browser/themes/shared/incontentprefs/preferences.inc.css
@@ -151,6 +151,11 @@ treecol {
   margin-right: 4px !important;
 }
 
+#defaultFontSizeLabel {
+  /* !important needed to override common !important rule */
+  -moz-margin-start: 4px !important;
+}
+
 /* Applications Pane Styles */
 
 #applicationsContent {