diff --git a/docs/quickstart.rst b/docs/quickstart.rst
index 526d8f7b..6d641d26 100644
--- a/docs/quickstart.rst
+++ b/docs/quickstart.rst
@@ -54,6 +54,24 @@ So what did that code do?
 
 To stop the server, hit control-C.
 
+.. _public-server:
+
+.. admonition:: Externally Visible Server
+
+   If you run the server you will notice that the server is only available
+   from your own computer, not from any other in the network.  This is the
+   default because in debugging mode a user of the application can execute
+   arbitrary Python code on your computer.  If you have `debug` disabled
+   or trust the users on your network, you can make the server publicly
+   available.
+
+   Just change the call of the :meth:`~flask.Flask.run` method to look
+   like this::
+
+       app.run(host='0.0.0.0')
+
+   This tells your operating system to listen on a public IP.
+
 
 Debug Mode
 ----------
diff --git a/docs/tutorial/setup.rst b/docs/tutorial/setup.rst
index 24b76561..1214c22f 100644
--- a/docs/tutorial/setup.rst
+++ b/docs/tutorial/setup.rst
@@ -57,13 +57,8 @@ without problems.  When you head over to the server you will get an 404
 page not found error because we don't have any views yet.  But we will
 focus on that a little later.  First we should get the database working.
 
-.. admonition:: Troubleshooting
+.. admonition:: Externally Visible Server
 
-   If you notice later that the browser cannot connect to the server
-   during development, you might want to try this line instead::
-
-       app.run(host='127.0.0.1')
-
-   In a nutshell: Werkzeug starts up as IPv6 on many operating systems by
-   default and not every browser is happy with that.  This forces IPv4
-   usage.
+   Want your server to be publically available?  Check out the
+   :ref:`externally visible server <public-server>` section for more
+   information.
diff --git a/flask.py b/flask.py
index 6d242aa1..1442650c 100644
--- a/flask.py
+++ b/flask.py
@@ -850,7 +850,7 @@ class Flask(_PackageBoundObject):
         """Converts the return value from a view function to a real
         response object that is an instance of :attr:`response_class`.
 
-        The following types are allowd for `rv`:
+        The following types are allowed for `rv`:
 
         ======================= ===========================================
         :attr:`response_class`  the object is returned unchanged
@@ -866,6 +866,11 @@ class Flask(_PackageBoundObject):
 
         :param rv: the return value from the view function
         """
+        if rv is None:
+            from warnings import warn
+            warn(Warning('View function did not return a response'),
+                 stacklevel=2)
+            return u''
         if isinstance(rv, self.response_class):
             return rv
         if isinstance(rv, basestring):
diff --git a/tests/flask_tests.py b/tests/flask_tests.py
index 15b53651..7851bc75 100644
--- a/tests/flask_tests.py
+++ b/tests/flask_tests.py
@@ -15,6 +15,7 @@ import sys
 import flask
 import unittest
 import tempfile
+import warnings
 
 
 example_path = os.path.join(os.path.dirname(__file__), '..', 'examples')
@@ -224,6 +225,19 @@ class BasicFunctionalityTestCase(unittest.TestCase):
             assert flask.url_for('static', filename='index.html') \
                 == '/static/index.html'
 
+    def test_none_response(self):
+        warnings.filterwarnings('error', 'View function did not return')
+        app = flask.Flask(__name__)
+        @app.route('/')
+        def test():
+            return None
+        try:
+            app.test_client().get('/')
+        except Warning:
+            pass
+        else:
+            assert "Expected warning"
+
 
 class JSONTestCase(unittest.TestCase):