--- a/browser/locales/en-US/chrome/browser/browser.dtd
+++ b/browser/locales/en-US/chrome/browser/browser.dtd
@@ -852,22 +852,31 @@ you can use these alternative items. Oth
 <!ENTITY customizeMode.lwthemes.myThemes "My Themes">
 <!ENTITY customizeMode.lwthemes.recommended "Recommended">
 <!ENTITY customizeMode.lwthemes.menuManage "Manage">
 <!ENTITY customizeMode.lwthemes.menuManage.accessKey "M">
 <!ENTITY customizeMode.lwthemes.menuGetMore "Get More Themes">
 <!ENTITY customizeMode.lwthemes.menuGetMore.accessKey "G">
 <!ENTITY customizeMode.emptyOverflowList.description "Drag and drop items here to keep them within reach but out of your toolbar…">
 <!ENTITY customizeMode.uidensity "Density">
+<!-- LOCALIZATION NOTE (customizeMode.uidensity.menuNormal.*):
+     “Normal” is displayed in the Customize screen, under the Density menu. -->
 <!ENTITY customizeMode.uidensity.menuNormal.label "Normal">
 <!ENTITY customizeMode.uidensity.menuNormal.tooltip "Normal">
 <!ENTITY customizeMode.uidensity.menuNormal.accessKey "N">
+<!-- LOCALIZATION NOTE (customizeMode.uidensity.menuCompact.*):
+     “Compact” is displayed in the Customize screen, under the Density menu.
+     It’s an adjective (Density -> Compact). -->
 <!ENTITY customizeMode.uidensity.menuCompact.label "Compact">
 <!ENTITY customizeMode.uidensity.menuCompact.tooltip "Compact">
 <!ENTITY customizeMode.uidensity.menuCompact.accessKey "C">
+<!-- LOCALIZATION NOTE (customizeMode.uidensity.menuTouch.*):
+     “Touch” is displayed in the Customize screen, under the Density menu.
+     It’s an adjective (Density -> Touch), and it means that control layout is
+     optimized for touch devices. -->
 <!ENTITY customizeMode.uidensity.menuTouch.label "Touch">
 <!ENTITY customizeMode.uidensity.menuTouch.tooltip "Touch">
 <!ENTITY customizeMode.uidensity.menuTouch.accessKey "T">
 <!ENTITY customizeMode.uidensity.autoTouchMode.checkbox.label "Use Touch for Tablet Mode">
 
 <!ENTITY getUserMedia.selectCamera.label "Camera to share:">
 <!ENTITY getUserMedia.selectCamera.accesskey "C">
 <!ENTITY getUserMedia.selectMicrophone.label "Microphone to share:">