Minor rewording and fixed one reference

Author: javiereguiluz

quick_tour/the_big_picture.rst

@@ -91,10 +91,11 @@ main concepts. Go to the following URL to be greeted by Symfony2 (replace
 
 .. note::
 
-    Instead of the greeting page, you may see a blank or error page. This is
-    caused by a directory permission misconfiguration. There are several possible
-    solutions depending on your operating system. All of them are explained in
-    the :ref:`book-installation-permission` section of the official book.
+    Instead of the greeting page, you may see a blank page or an error page.
+    This is caused by a directory permission misconfiguration. There are several
+    possible solutions depending on your operating system. All of them are
+    explained in the :ref:`book-installation-permissions` section of the
+    official book.
 
 What's going on here? Have a look at each part of the URL: