typo fix in Responding to Successful Logins section

Signed-off-by: Armin Ronacher <armin.ronacher@active-4.com>
diff --git a/docs/index.rst b/docs/index.rst
index 35e9602..7d2d789 100644
--- a/docs/index.rst
+++ b/docs/index.rst
@@ -121,7 +121,7 @@
 -------------------------------
 
 Next we have to define a function that is called after the login was
-successful.  The resonsibility of that function is to remember the user
+successful.  The responsibility of that function is to remember the user
 that just logged in and to figure out if it's a new user to the system or
 one with an existing profile (if you want to use profiles).