diff -r d499189e7758 Doc/library/string.rst
--- a/Doc/library/string.rst	Fri Apr 19 22:38:58 2013 -0400
+++ b/Doc/library/string.rst	Fri Apr 19 23:03:29 2013 -0400
@@ -203,26 +203,27 @@
       conversion: "r" | "s" | "a"
       format_spec: <described in the next section>
 
-In less formal terms, the replacement field can start with a *field_name* that specifies
-the object whose value is to be formatted and inserted
-into the output instead of the replacement field.
-The *field_name* is optionally followed by a  *conversion* field, which is
-preceded by an exclamation point ``'!'``, and a *format_spec*, which is preceded
-by a colon ``':'``.  These specify a non-default format for the replacement value.
+In less formal terms, the replacement field can start with a *field_name* that
+specifies the object whose value is to be formatted and inserted into the
+output instead of the replacement field.  The *field_name* is optionally
+followed by a  *conversion* field, which is preceded by an exclamation point
+``'!'``, and a *format_spec*, which is preceded by a colon ``':'``.  These
+specify a non-default format for the replacement value.
 
 See also the :ref:`formatspec` section.
 
 The *field_name* itself begins with an *arg_name* that is either a number or a
-keyword.  If it's a number, it refers to a positional argument, and if it's a keyword,
-it refers to a named keyword argument.  If the numerical arg_names in a format string
-are 0, 1, 2, ... in sequence, they can all be omitted (not just some)
-and the numbers 0, 1, 2, ... will be automatically inserted in that order.
-Because *arg_name* is not quote-delimited, it is not possible to specify arbitrary
-dictionary keys (e.g., the strings ``'10'`` or ``':-]'``) within a format string.
-The *arg_name* can be followed by any number of index or
-attribute expressions. An expression of the form ``'.name'`` selects the named
-attribute using :func:`getattr`, while an expression of the form ``'[index]'``
-does an index lookup using :func:`__getitem__`.
+keyword.  If it's a number, it refers to a positional argument, and if it's a
+keyword, it refers to a named keyword argument.  If the numerical arg_names in
+a format string are 0, 1, 2, ... in sequence, they can all be omitted (not
+just some) and the numbers 0, 1, 2, ... will be automatically inserted in that
+order.  Numerical arg_names that are negative and negative slices are not
+supported.  Because *arg_name* is not quote-delimited, it is not possible to
+specify arbitrary dictionary keys (e.g., the strings ``'10'`` or ``':-]'``)
+within a format string.  The *arg_name* can be followed by any number of index
+or attribute expressions. An expression of the form ``'.name'`` selects the
+named attribute using :func:`getattr`, while an expression of the form
+``'[index]'`` does an index lookup using :func:`__getitem__`.
 
 .. versionchanged:: 3.1
    The positional argument specifiers can be omitted, so ``'{} {}'`` is