Fix error in errata

Author: marijnh

html/errata.html

@@ -66,7 +66,7 @@ <h2>Chapter 11</h2>
 <h2>Chapter 12</h2>
 
 <p><strong>Page 209</strong> (The Web): In the third paragraph I claim
-that the U in “URL” stands for <em>Universal</em>, whereas it actual
+that the U in “URL” stands for <em>Universal</em>, whereas it actually
 stands for <em>Uniform</em>.</p>
 
 <h2>Chapter 14</h2>