diff --git a/Lib/urllib2.py b/Lib/urllib2.py
index 046470a..7c73f81 100644
--- a/Lib/urllib2.py
+++ b/Lib/urllib2.py
@@ -487,7 +487,9 @@
     def http_response(self, request, response):
         code, msg, hdrs = response.code, response.msg, response.info()
 
-        if code not in (200, 206):
+        # According to RFC 2616, "2xx" code indicates that the client's 
+        # request was successfully received, understood, and accepted.
+        if not (200 <= code < 300):
             response = self.parent.error(
                 'http', request, response, code, msg, hdrs)