Mark some errata as fixed in the 3rd reprint

Author: marijnh

html/errata.html

@@ -32,7 +32,7 @@ <h2>Chapter 2</h2>
 
 <h2>Chapter 5</h2>
 
-<p><strong>Page 91</strong> <em>Composability</em>: Due to an initial
+<p><strong>Page 91</strong> (3rd) <em>Composability</em>: Due to an initial
 mistake in the script data set, the results of the computations on
 this page differ from the ones with the current, corrected data. The
 average year for living scripts should be 1165, the average for
@@ -65,7 +65,7 @@ <h2>Chapter 14</h2>
 
 <h2>Chapter 15</h2>
 
-<p><strong>Page 258</strong> <em>Load Event</em>: The description of
+<p><strong>Page 258</strong> (3rd) <em>Load Event</em>: The description of
 the <code>beforeunload</code> claims that you just need to return a
 string from your event handler. For handlers registered
 with <code>addEventListener</code> you, in fact, need to
@@ -86,12 +86,12 @@ <h2>Chapter 20</h2>
 
 <h2>Chapter 21</h2>
 
-<p><strong>Page 373</strong> <em>HTTP Interface</em>: There is a
+<p><strong>Page 373</strong> (3rd) <em>HTTP Interface</em>: There is a
 superfluous closing brace at the end of the example JSON snippet.</p>
 
 <h2>Exercise Hints</h2>
 
-<p><strong>Page 414</strong> <em>A Modular Robot</em>:
+<p><strong>Page 414</strong> (3rd) <em>A Modular Robot</em>:
 The <code>dijkstrajs</code> package name is misspelled
 as <code>dijkstajs</code>.