diff --git a/Doc/library/marshal.rst b/Doc/library/marshal.rst
index 0cf69b4..bc43184 100644
--- a/Doc/library/marshal.rst
+++ b/Doc/library/marshal.rst
@@ -45,12 +45,6 @@
 (they will cause infinite loops).
 
 .. warning::
-
-   Some unsupported types such as subclasses of builtins will appear to marshal
-   and unmarshal correctly, but in fact, their type will change and the
-   additional subclass functionality and instance attributes will be lost.
-
-.. warning::
    
    On machines where C's ``long int`` type has more than 32 bits (such as the
    DEC Alpha), it is possible to create plain Python integers that are longer
diff --git a/Doc/library/stdtypes.rst b/Doc/library/stdtypes.rst
index 9073bca..d6a853b 100644
--- a/Doc/library/stdtypes.rst
+++ b/Doc/library/stdtypes.rst
@@ -1418,6 +1418,13 @@
 
    Test *x* for non-membership in *s*.
 
+.. method:: set.isdisjoint(other)
+
+   Return True if the set has no elements in common with *other*.
+   Sets are disjoint if and only if their interesection is the empty set.
+
+   .. versionadded:: 2.6
+
 .. method:: set.issubset(other)
             set <= other
 
diff --git a/Doc/tutorial/introduction.rst b/Doc/tutorial/introduction.rst
index 30adac9..4226ffd 100644
--- a/Doc/tutorial/introduction.rst
+++ b/Doc/tutorial/introduction.rst
@@ -507,8 +507,9 @@
 
 The built-in function :func:`len` also applies to lists::
 
+   >>> a = ['a', 'b', 'c', 'd']
    >>> len(a)
-   8
+   4
 
 It is possible to nest lists (create lists containing other lists), for
 example::