diff --git a/prologue/typography.xml b/prologue/typography.xml
index e4c7b5c78..6b7d6437d 100644
--- a/prologue/typography.xml
+++ b/prologue/typography.xml
@@ -37,6 +37,12 @@
   the result of commands issued.  This format is also used to show filenames,
   such as <filename>/etc/ld.so.conf</filename>.</para>
 
+  <note>
+    <para>Please configure your browser to display fixed-width text with
+    a good monospaced font, with which you can distinguish the glyphs of
+    <literal>Il1</literal> or <literal>O0</literal> clearly.</para>
+  </note>
+
   <para><emphasis>Emphasis</emphasis></para>
 
   <para>This form of text is used for several purposes in the book. Its main