--- a/firefox-devel.rst	Tue Oct 22 22:52:02 2013 +0300
+++ b/firefox-devel.rst	Tue Oct 22 22:59:22 2013 +0300
@@ -112,7 +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: