diff --git a/www/403.php b/www/403.php
index 5c8a517b..1199296a 100644
--- a/www/403.php
+++ b/www/403.php
@@ -3,7 +3,7 @@
 	<section class="narrow has-hero">
 		<hgroup>
 			<h1>You Don’t Have Permission to View This Page</h1>
-			<h2>This is 403 error.</h2>
+			<h2>This is a 403 error.</h2>
 		</hgroup>
 		<picture data-caption="The Guard Room. David Teniers II, 1642">
 			<source srcset="/images/guard-room@2x.avif 2x, /images/guard-room.avif 1x" type="image/avif"/>
diff --git a/www/404.php b/www/404.php
index fae63e1d..44343d1e 100644
--- a/www/404.php
+++ b/www/404.php
@@ -3,7 +3,7 @@
 	<section class="narrow has-hero">
 		<hgroup>
 			<h1>We Couldn’t Find That Document</h1>
-			<h2>This is 404 error.</h2>
+			<h2>This is a 404 error.</h2>
 		</hgroup>
 		<picture data-caption="Blind Orion Searching for the Rising Sun. Nicolas Poussin, 1658">
 			<source srcset="/images/blind-orion@2x.avif 2x, /images/blind-orion.avif 1x" type="image/avif"/>
diff --git a/www/451.php b/www/451.php
index 9db0a022..de3106c1 100644
--- a/www/451.php
+++ b/www/451.php
@@ -3,7 +3,7 @@
 	<section class="narrow has-hero">
 		<hgroup>
 			<h1>This Ebook Is No Longer Available</h1>
-			<h2>This is 451 error.</h2>
+			<h2>This is a 451 error.</h2>
 		</hgroup>
 		<picture data-caption="The Preaching of St. Paul at Ephesus. Eustache Le Sueur, 1649">
 			<source srcset="/images/the-preaching-of-st-paul-at-ephesus@2x.avif 2x, /images/the-preaching-of-st-paul-at-ephesus.avif 1x" type="image/avif"/>