diff --git a/PIL/ImageFile.py b/PIL/ImageFile.py
index 7406f5752..423a4363f 100644
--- a/PIL/ImageFile.py
+++ b/PIL/ImageFile.py
@@ -610,7 +610,7 @@ class PyDecoder(object):
             (x0, y0, x1, y1) = (0, 0, 0, 0)
 
         
-        if x0 ==0 and x1 ==0:
+        if x0 == 0 and x1 == 0:
             self.state.xsize, self.state.ysize = self.im.size
         else:
             self.state.xoff = x0
@@ -619,7 +619,7 @@ class PyDecoder(object):
             self.state.ysize = y1 - y0
 
         if self.state.xsize <= 0 or self.state.ysize <= 0:
-            raise ValueError("Size Cannot be Negative")
+            raise ValueError("Size cannot be negative")
         
         if (self.state.xsize + self.state.xoff > self.im.size[0] or
             self.state.ysize + self.state.yoff > self.im.size[1]):
diff --git a/PIL/MspImagePlugin.py b/PIL/MspImagePlugin.py
index 8f6e705ae..11e983a3a 100644
--- a/PIL/MspImagePlugin.py
+++ b/PIL/MspImagePlugin.py
@@ -90,13 +90,13 @@ class MspDecoder(ImageFile.PyDecoder):
     #
     # Pseudocode of the decoder:
     # Read a BYTE value as the RunType
-	#  If the RunType value is zero
-	# 	Read next byte as the RunCount
-	# 	Read the next byte as the RunValue
-	# 	Write the RunValue byte RunCount times
-	#  If the RunType value is non-zero
-	# 	Use this value as the RunCount
-	# 	Read and write the next RunCount bytes literally
+    #  If the RunType value is zero
+    #   Read next byte as the RunCount
+    #   Read the next byte as the RunValue
+    #   Write the RunValue byte RunCount times
+    #  If the RunType value is non-zero
+    #   Use this value as the RunCount
+    #   Read and write the next RunCount bytes literally
     # 
     #  e.g.:
     #  0x00 03 ff 05 00 01 02 03 04
@@ -113,7 +113,6 @@ class MspDecoder(ImageFile.PyDecoder):
         img = io.BytesIO()
         blank_line = bytearray((0xff,)*((self.state.xsize+7)//8))
         try:
-            last_pos = 0
             self.fd.seek(32)
             rowmap = struct.unpack_from("<%dH" % (self.state.ysize),
                                         self.fd.read(self.state.ysize*2))
diff --git a/Tests/test_file_msp.py b/Tests/test_file_msp.py
index cfcca0b1a..dbffe7369 100644
--- a/Tests/test_file_msp.py
+++ b/Tests/test_file_msp.py
@@ -1,6 +1,6 @@
 from helper import unittest, PillowTestCase, hopper
 
-from PIL import Image, ImageFile, MspImagePlugin
+from PIL import Image, MspImagePlugin
 
 import os
 
diff --git a/docs/handbook/writing-your-own-file-decoder.rst b/docs/handbook/writing-your-own-file-decoder.rst
index 07468dc4a..0292a7880 100644
--- a/docs/handbook/writing-your-own-file-decoder.rst
+++ b/docs/handbook/writing-your-own-file-decoder.rst
@@ -26,14 +26,14 @@ Pillow decodes files in 2 stages:
    called, which sets up a decoder for each tile and feeds the data to
    it.
 
-A image plug-in should contain a format handler derived from the
+An image plug-in should contain a format handler derived from the
 :py:class:`PIL.ImageFile.ImageFile` base class. This class should
 provide an :py:meth:`_open` method, which reads the file header and
 sets up at least the :py:attr:`~PIL.Image.Image.mode` and
 :py:attr:`~PIL.Image.Image.size` attributes. To be able to load the
 file, the method must also create a list of :py:attr:`tile`
 descriptors, which contain a decoder name, extents of the tile, and
-any decoder specific data. The format handler class must be explicitly
+any decoder-specific data. The format handler class must be explicitly
 registered, via a call to the :py:mod:`~PIL.Image` module.
 
 .. note:: For performance reasons, it is important that the
@@ -403,8 +403,8 @@ Python file decoders should derive from
 :py:class:`PIL.ImageFile.PyDecoder` and should at least override the
 decode method. File decoders should be registered using
 :py:meth:`PIL.Image.register_decoder`. As in the C implementation of
-the file decoders, there are three stages in the lifetime of a Python
-based file decoder:
+the file decoders, there are three stages in the lifetime of a
+Python-based file decoder:
 
 1. Setup: Pillow looks for the decoder in the registry, then
    instantiates the class.