--- a/toolkit/components/console/hudservice/HUDService.jsm
+++ b/toolkit/components/console/hudservice/HUDService.jsm
@@ -2545,16 +2545,25 @@ HUD_SERVICE.prototype =
                 data = [ httpActivity.url,
                          httpActivity.response.status ];
 
                 msgObject.messageNode.appendChild(
                   msgObject.textFactory(
                     msgObject.prefix +
                     self.getFormatStr("networkUrlWithStatus", data) + "\n"));
 
+                let status = parseInt(httpActivity.response.status.
+                  replace(/^HTTP\/\d\.\d (\d+).+$/, "$1"));
+
+                if (status) {
+                  msgObject.messageNode.classList.
+                    add((status >= 400 && status < 600) ?
+                      "hud-error" : "hud-info");
+                }
+
                 break;
 
               case activityDistributor.ACTIVITY_SUBTYPE_TRANSACTION_CLOSE:
                 let timing = httpActivity.timing;
                 let requestDuration =
                   Math.round((timing.RESPONSE_COMPLETE -
                                 timing.REQUEST_HEADER) / 1000);
 
@@ -2859,27 +2868,29 @@ HUD_SERVICE.prototype =
     }
     return sequencer(aInt);
   },
 
   scriptErrorFlags: {
     0: "error",
     1: "warn",
     2: "exception",
-    4: "strict"
+    4: "error", // strict error
+    5: "warn", // strict warning
   },
 
   /**
    * replacement strings (L10N)
    */
   scriptMsgLogLevel: {
     0: "typeError",
     1: "typeWarning",
     2: "typeException",
-    4: "typeStrict",
+    4: "typeError", // strict error
+    5: "typeStrict", // strict warning
   },
 
   /**
    * Closes the Console, if any, that resides on the given tab.
    *
    * @param nsIDOMNode aTab
    *        The tab on which to close the console.
    * @returns void

--- a/toolkit/components/console/hudservice/tests/browser/Makefile.in
+++ b/toolkit/components/console/hudservice/tests/browser/Makefile.in
@@ -100,16 +100,17 @@ include $(topsrcdir)/config/rules.mk
 	browser_webconsole_bug_595934_message_categories.js \
 	browser_webconsole_bug_601352_scroll.js \
 	browser_webconsole_bug_592442_closing_brackets.js \
 	browser_webconsole_bug_593003_iframe_wrong_hud.js \
 	browser_webconsole_bug_601909_remember_height.js \
 	browser_webconsole_bug_613013_console_api_iframe.js \
 	browser_webconsole_bug_597756_reopen_closed_tab.js \
 	browser_webconsole_bug_600183_charset.js \
+	browser_webconsole_bug_601177_log_levels.js \
 	head.js \
 	$(NULL)
 
 _BROWSER_TEST_PAGES = \
 	test-console.html \
 	test-network.html \
 	test-network-request.html \
 	test-mutation.html \
@@ -136,15 +137,17 @@ include $(topsrcdir)/config/rules.mk
 	test-bug-595934-malformedxml.xhtml \
 	test-bug-595934-svg.xhtml \
 	test-bug-597136-external-script-errors.html \
 	test-bug-597136-external-script-errors.js \
 	test-bug-613013-console-api-iframe.html \
 	test-bug-597756-reopen-closed-tab.html \
 	test-bug-600183-charset.html \
 	test-bug-600183-charset.html^headers^ \
+	test-bug-601177-log-levels.html \
+	test-bug-601177-log-levels.js \
 	$(NULL)
 
 libs:: $(_BROWSER_TEST_FILES)
 	$(INSTALL) $(foreach f,$^,"$f") $(DEPTH)/_tests/testing/mochitest/browser/$(relativesrcdir)
 
 libs:: $(_BROWSER_TEST_PAGES)
 	$(INSTALL) $(foreach f,$^,"$f") $(DEPTH)/_tests/testing/mochitest/browser/$(relativesrcdir)

new file mode 100644
--- /dev/null
+++ b/toolkit/components/console/hudservice/tests/browser/browser_webconsole_bug_601177_log_levels.js
@@ -0,0 +1,73 @@
+/* vim:set ts=2 sw=2 sts=2 et: */
+/* ***** BEGIN LICENSE BLOCK *****
+ * Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ *
+ * Contributor(s):
+ *  Mihai Șucan <mihai.sucan@gmail.com>
+ *
+ * ***** END LICENSE BLOCK ***** */
+
+const TEST_URI = "http://example.com/browser/toolkit/components/console/hudservice/tests/browser/test-bug-601177-log-levels.html";
+
+let msgs;
+
+function onContentLoaded()
+{
+  let hudId = HUDService.getHudIdByWindow(content);
+  let HUD = HUDService.hudReferences[hudId];
+  msgs = HUD.outputNode.querySelectorAll(".hud-group > *");
+
+  ok(findEntry("hud-info", "test-bug-601177-log-levels.html"),
+    "found test-bug-601177-log-levels.html");
+
+  ok(findEntry("hud-info", "test-bug-601177-log-levels.js"),
+    "found test-bug-601177-log-levels.js");
+
+  ok(findEntry("hud-info", "test-image.png"),
+    "found test-image.png");
+
+  ok(findEntry("hud-error", "foobar-known-to-fail.png"),
+    "found foobar-known-to-fail.png");
+
+  ok(findEntry("hud-exception", "foobarBug601177exception"),
+    "found exception");
+
+  ok(findEntry("hud-warn", "undefinedPropertyBug601177"),
+    "found strict warning");
+
+  msgs = null;
+  Services.prefs.setBoolPref("javascript.options.strict", false);
+  finishTest();
+}
+
+function findEntry(aClass, aString)
+{
+  for (let i = 0, n = msgs.length; i < n; i++) {
+    if (msgs[i].classList.contains(aClass) &&
+        msgs[i].textContent.indexOf(aString) > -1) {
+      return true;
+    }
+  }
+  return false;
+}
+
+function test()
+{
+  addTab("data:text/html,Web Console test for bug 601177: log levels");
+
+  Services.prefs.setBoolPref("javascript.options.strict", true);
+
+  browser.addEventListener("load", function(aEvent) {
+    browser.removeEventListener(aEvent.type, arguments.callee, true);
+
+    openConsole();
+
+    browser.addEventListener("load", function(aEvent) {
+      browser.removeEventListener(aEvent.type, arguments.callee, true);
+      executeSoon(onContentLoaded);
+    }, true);
+    content.location = TEST_URI;
+  }, true);
+}
+

new file mode 100644
--- /dev/null
+++ b/toolkit/components/console/hudservice/tests/browser/test-bug-601177-log-levels.html
@@ -0,0 +1,19 @@
+<!DOCTYPE HTML>
+<html dir="ltr" xml:lang="en-US" lang="en-US">
+  <head>
+    <title>Web Console test for bug 601177: network messages</title>
+    <script src="test-bug-601177-log-levels.js" type="text/javascript"></script>
+    <script type="text/javascript"><!--
+      window.undefinedPropertyBug601177;
+    // --></script>
+    <!--
+       - Any copyright is dedicated to the Public Domain.
+       - http://creativecommons.org/publicdomain/zero/1.0/
+       -->
+  </head>
+  <body>
+    <h1>Web Console test for bug 601177: network messages</h1>
+    <img src="test-image.png?bug601177">
+    <img src="foobar-known-to-fail.png?bug601177">
+  </body>
+</html>

new file mode 100644
--- /dev/null
+++ b/toolkit/components/console/hudservice/tests/browser/test-bug-601177-log-levels.js
@@ -0,0 +1,6 @@
+/*
+ * Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+window.foobarBug601177exception();