diff --git a/Lib/test/test_urllib2.py b/Lib/test/test_urllib2.py
index 8d1363d..5710444 100644
--- a/Lib/test/test_urllib2.py
+++ b/Lib/test/test_urllib2.py
@@ -493,11 +493,11 @@
             r = MockResponse(200, "OK", {}, "")
             newreq = h.do_request_(req)
             if data is None:  # GET
-                self.assert_("Content-Length" not in req.unredirected_hdrs)
-                self.assert_("Content-Type" not in req.unredirected_hdrs)
+                self.assert_("Content-length" not in req.unredirected_hdrs)
+                self.assert_("Content-type" not in req.unredirected_hdrs)
             else:  # POST
-                self.assertEqual(req.unredirected_hdrs["Content-Length"], "0")
-                self.assertEqual(req.unredirected_hdrs["Content-Type"],
+                self.assertEqual(req.unredirected_hdrs["Content-length"], "0")
+                self.assertEqual(req.unredirected_hdrs["Content-type"],
                              "application/x-www-form-urlencoded")
             # XXX the details of Host could be better tested
             self.assertEqual(req.unredirected_hdrs["Host"], "example.com")
@@ -509,8 +509,8 @@
             req.add_unredirected_header("Host", "baz")
             req.add_unredirected_header("Spam", "foo")
             newreq = h.do_request_(req)
-            self.assertEqual(req.unredirected_hdrs["Content-Length"], "foo")
-            self.assertEqual(req.unredirected_hdrs["Content-Type"], "bar")
+            self.assertEqual(req.unredirected_hdrs["Content-length"], "foo")
+            self.assertEqual(req.unredirected_hdrs["Content-type"], "bar")
             self.assertEqual(req.unredirected_hdrs["Host"], "baz")
             self.assertEqual(req.unredirected_hdrs["Spam"], "foo")
 
diff --git a/Lib/urllib.py b/Lib/urllib.py
index d4573c6..d1c50f6 100644
--- a/Lib/urllib.py
+++ b/Lib/urllib.py
@@ -118,7 +118,7 @@
         self.proxies = proxies
         self.key_file = x509.get('key_file')
         self.cert_file = x509.get('cert_file')
-        self.addheaders = [('User-Agent', self.version)]
+        self.addheaders = [('User-agent', self.version)]
         self.__tempfiles = []
         self.__unlink = os.unlink # See cleanup()
         self.tempcache = None
@@ -314,8 +314,8 @@
         h = httplib.HTTP(host)
         if data is not None:
             h.putrequest('POST', selector)
-            h.putheader('Content-Type', 'application/x-www-form-urlencoded')
-            h.putheader('Content-Length', '%d' % len(data))
+            h.putheader('Content-type', 'application/x-www-form-urlencoded')
+            h.putheader('Content-length', '%d' % len(data))
         else:
             h.putrequest('GET', selector)
         if proxy_auth: h.putheader('Proxy-Authorization', 'Basic %s' % proxy_auth)
@@ -400,9 +400,9 @@
                               cert_file=self.cert_file)
             if data is not None:
                 h.putrequest('POST', selector)
-                h.putheader('Content-Type',
+                h.putheader('Content-type',
                             'application/x-www-form-urlencoded')
-                h.putheader('Content-Length', '%d' % len(data))
+                h.putheader('Content-length', '%d' % len(data))
             else:
                 h.putrequest('GET', selector)
             if proxy_auth: h.putheader('Proxy-Authorization: Basic %s' % proxy_auth)
@@ -584,7 +584,7 @@
             data = base64.decodestring(data)
         else:
             data = unquote(data)
-        msg.append('Content-Length: %d' % len(data))
+        msg.append('Content-length: %d' % len(data))
         msg.append('')
         msg.append(data)
         msg = '\n'.join(msg)
diff --git a/Lib/urllib2.py b/Lib/urllib2.py
index bc6ee4b..0434a51 100644
--- a/Lib/urllib2.py
+++ b/Lib/urllib2.py
@@ -254,11 +254,11 @@
 
     def add_header(self, key, val):
         # useful for something like authentication
-        self.headers[key.title()] = val
+        self.headers[key.capitalize()] = val
 
     def add_unredirected_header(self, key, val):
         # will not be added to a redirected request
-        self.unredirected_hdrs[key.title()] = val
+        self.unredirected_hdrs[key.capitalize()] = val
 
     def has_header(self, header_name):
         return (header_name in self.headers or
@@ -277,7 +277,7 @@
 class OpenerDirector:
     def __init__(self):
         client_version = "Python-urllib/%s" % __version__
-        self.addheaders = [('User-Agent', client_version)]
+        self.addheaders = [('User-agent', client_version)]
         # manage the individual handlers
         self.handlers = []
         self.handle_open = {}
@@ -592,7 +592,7 @@
             user, password = user_pass.split(':', 1)
             user_pass = base64.encodestring('%s:%s' % (unquote(user),
                                             unquote(password))).strip()
-            req.add_header('Proxy-Authorization', 'Basic ' + user_pass)
+            req.add_header('Proxy-authorization', 'Basic ' + user_pass)
         host = unquote(host)
         req.set_proxy(host, type)
         if orig_type == type:
@@ -755,7 +755,7 @@
 
 class ProxyBasicAuthHandler(AbstractBasicAuthHandler, BaseHandler):
 
-    auth_header = 'Proxy-Authorization'
+    auth_header = 'Proxy-authorization'
 
     def http_error_407(self, req, fp, code, msg, headers):
         host = req.get_host()
@@ -955,20 +955,20 @@
 
         if request.has_data():  # POST
             data = request.get_data()
-            if not request.has_header('Content-Type'):
+            if not request.has_header('Content-type'):
                 request.add_unredirected_header(
-                    'Content-Type',
+                    'Content-type',
                     'application/x-www-form-urlencoded')
-            if not request.has_header('Content-Length'):
+            if not request.has_header('Content-length'):
                 request.add_unredirected_header(
-                    'Content-Length', '%d' % len(data))
+                    'Content-length', '%d' % len(data))
 
         scheme, sel = splittype(request.get_selector())
         sel_host, sel_path = splithost(sel)
         if not request.has_header('Host'):
             request.add_unredirected_header('Host', sel_host or host)
         for name, value in self.parent.addheaders:
-            name = name.title()
+            name = name.capitalize()
             if not request.has_header(name):
                 request.add_unredirected_header(name, value)
 
@@ -1145,7 +1145,7 @@
         modified = email.Utils.formatdate(stats.st_mtime, usegmt=True)
         mtype = mimetypes.guess_type(file)[0]
         headers = mimetools.Message(StringIO(
-            'Content-Type: %s\nContent-Length: %d\nLast-Modified: %s\n' %
+            'Content-type: %s\nContent-length: %d\nLast-modified: %s\n' %
             (mtype or 'text/plain', size, modified)))
         if host:
             host, port = splitport(host)
@@ -1198,9 +1198,9 @@
             headers = ""
             mtype = mimetypes.guess_type(req.get_full_url())[0]
             if mtype:
-                headers += "Content-Type: %s\n" % mtype
+                headers += "Content-type: %s\n" % mtype
             if retrlen is not None and retrlen >= 0:
-                headers += "Content-Length: %d\n" % retrlen
+                headers += "Content-length: %d\n" % retrlen
             sf = StringIO(headers)
             headers = mimetools.Message(sf)
             return addinfourl(fp, headers, req.get_full_url())