--- a/browser/devtools/shared/DeveloperToolbar.jsm
+++ b/browser/devtools/shared/DeveloperToolbar.jsm
@@ -621,27 +621,26 @@ function DT__updateErrorsCount(aChangedT
     return;
   }
 
   let errors = this._errorsCount[tabId];
   let warnings = this._warningsCount[tabId];
   let btn = this._errorCounterButton;
   if (errors) {
     let errorsText = toolboxStrings
-                     .GetStringFromName("toolboxToggleButton.errorsCount");
-    errorsText = PluralForm.get(errors, errorsText);
+                     .GetStringFromName("toolboxToggleButton.errors");
+    errorsText = PluralForm.get(errors, errorsText).replace("#1", errors);
 
     let warningsText = toolboxStrings
-                       .GetStringFromName("toolboxToggleButton.warningsCount");
-    warningsText = PluralForm.get(warnings, warningsText);
+                       .GetStringFromName("toolboxToggleButton.warnings");
+    warningsText = PluralForm.get(warnings, warningsText).replace("#1", warnings);
 
     let tooltiptext = toolboxStrings
-                      .formatStringFromName("toolboxToggleButton.tooltiptext",
-                                            [errors, errorsText, warnings,
-                                             warningsText], 4);
+                      .formatStringFromName("toolboxToggleButton.tooltip",
+                                            [errorsText, warningsText], 2);
 
     btn.setAttribute("error-count", errors);
     btn.setAttribute("tooltiptext", tooltiptext);
   } else {
     btn.removeAttribute("error-count");
     btn.setAttribute("tooltiptext", btn._defaultTooltipText);
   }
 };

--- a/browser/locales/en-US/chrome/browser/devtools/toolbox.properties
+++ b/browser/locales/en-US/chrome/browser/devtools/toolbox.properties
@@ -1,10 +1,22 @@
 toolboxDockButtons.bottom.tooltip=Dock to bottom of browser window
 toolboxDockButtons.side.tooltip=Dock to side of browser window
 toolboxDockButtons.window.tooltip=Show in separate window
 
-# LOCALIZATION NOTE (toolboxToggleButton): These strings are used for the button
-# that allows users to open/close the developer tools. You can find this button
-# on the developer toolbar.
-toolboxToggleButton.errorsCount=error;errors
-toolboxToggleButton.warningsCount=warning;warnings
-toolboxToggleButton.tooltiptext=%S %S, %S %S.\nClick to toggle the developer tools.
+# LOCALIZATION NOTE (toolboxToggleButton.errors): Semi-colon list of plural
+# forms.
+# See: http://developer.mozilla.org/en/docs/Localization_and_Plurals
+# #1 number of errors in the current web page
+toolboxToggleButton.errors=#1 error;#1 errors
+
+# LOCALIZATION NOTE (toolboxToggleButton.warnings): Semi-colon list of plural
+# forms.
+# See: http://developer.mozilla.org/en/docs/Localization_and_Plurals
+# #1 number of warnings in the current web page
+toolboxToggleButton.warnings=#1 warning;#1 warnings
+
+# LOCALIZATION NOTE (toolboxToggleButton.tooltip): This string is shown
+# as tooltip in the developer toolbar to open/close the developer tools.
+# It's using toolboxToggleButton.errors as first and
+# toolboxToggleButton.warnings as second argument to show the number of errors
+# and warnings.
+toolboxToggleButton.tooltip=%1$S, %2$S\nClick to toggle the developer tools.