There is a small mistake in the current version of the Customizing matplotlib (http://matplotlib.org/users/customizing.html) article.

In the current version the example matplolitbrc file says in the section where yticks are set

#xtick.major.left     : True   # draw y axis left major ticks
#xtick.major.right    : True   # draw y axis right major ticks
#xtick.minor.left     : True   # draw y axis left minor ticks
#xtick.minor.right    : True   # draw y axis right minor ticks

while it should of course be ytick.m......

While this is a pretty obvious thing, someone might still want to change it at some point.
(I was unable to locate the file in the code on GitHub, so I can't make a pull request myself.)