Format fixes in html files of 2020

2020/endoh1/index.html

@@ -413,12 +413,12 @@ Location: <a href="../../location.html#JP">JP</a> - <em>Japan</em></li>
 <p>There is an alternate version provided by the author. See <a href="#alternate-code">Alternate
 code</a> below.</p>
 <h2 id="to-use">To use:</h2>
-<pre><code>    # IMPORTANT for macOS: run under Terminal.app
-
+<p><strong>IMPORTANT for macOS</strong>: run under Terminal.app.</p>
+<pre><code>
     ./prog</code></pre>
 <h2 id="try">Try:</h2>
-<pre><code>    # IMPORTANT for macOS: run under Terminal.app
-
+<p><strong>IMPORTANT for macOS</strong>: run under Terminal.app.</p>
+<pre><code>
     # Try resizing the terminal window before the first click.
 
     # Try resizing the terminal window after the first click.