--- a/firefox-devel.rst	Fri Oct 25 18:40:44 2013 +0300
+++ b/firefox-devel.rst	Fri Oct 25 23:25:42 2013 +0300
@@ -95,6 +95,11 @@
   // This will send more detailed information about installation and update problems to the Error Console.
   user_pref("extensions.logging.enabled", true);
   user_pref("dom.report_all_js_exceptions", true);
+  // This adds a "Browser Debugger" entry to the "Web Developer" submenu of the "Tools" menu.
+  // The Browser Debugger can be used to debug the JavaScript code of extensions.
+  user_pref("devtools.debugger.remote-enabled", true);
+  // Detect deprecated code use.
+  user_pref("devtools.errorconsole.deprecation_warnings", true);
 
 See:
 
@@ -107,7 +112,14 @@
 Instead of "Error Console" (press Ctrl+Shift+J) use "Web Console" (press
 Ctrl+Shift+K) in Firefox >=4.0::
 
-  'console.log()', 'console.info()', 'console.warn()', 'console.error()'.
+  console.log("str");
+  console.info("str is %s", "str");
+  console.warn("this is %o", this);
+  console.error("int: %i, float: %f, string: %s, object: %o", 2, .333, "str", this);
+
+To see stack-trace use::
+
+  console.log(new Error().stack);
 
 See: