--- a/browser/locales/en-US/chrome/browser/browser.dtd
+++ b/browser/locales/en-US/chrome/browser/browser.dtd
@@ -661,17 +661,17 @@ you can use these alternative items. Oth
 <!ENTITY fullZoomResetCmd.commandkey    "0">
 <!ENTITY fullZoomResetCmd.commandkey2   "">
 
 <!ENTITY fullZoomToggleCmd.label        "Zoom Text Only">
 <!ENTITY fullZoomToggleCmd.accesskey    "T">
 <!ENTITY fullZoom.label                 "Zoom">
 <!ENTITY fullZoom.accesskey             "Z">
 
-<!ENTITY sidebarCloseButton.tooltip     "Close Sidebar">
+<!ENTITY sidebarCloseButton.tooltip     "Close sidebar">
 
 <!ENTITY quitApplicationCmdWin2.label       "Exit">
 <!ENTITY quitApplicationCmdWin2.accesskey   "x">
 <!ENTITY quitApplicationCmdWin2.tooltip     "Exit &brandShorterName;">
 <!ENTITY goBackCmd.commandKey "[">
 <!ENTITY goForwardCmd.commandKey "]">
 <!ENTITY quitApplicationCmd.label       "Quit"> 
 <!ENTITY quitApplicationCmd.accesskey   "Q">