fix: Fix HTML validation warnings

layout/page.html

@@ -11,7 +11,7 @@
 
     <link rel="stylesheet" href="assets/css/index.css" />
     <link rel="stylesheet" href="{{ page_assets }}/css/main.css" />
-
+ 
     <!-- Mastodon -->
     <link rel="me" href="https://{{ mastodon_instance_url }}/{{ mastodon_handle }}" />
   </head>
@@ -19,7 +19,7 @@
     <div class="horizontal-center">
       <div class="vertical header">
 	<div id="header" class="horizontal">
-	  <img class="avatar" src="{{ page_assets }}/img/avatar.jpg" />
+	  <img class="avatar" src="{{ page_assets }}/img/avatar.jpg" alt="" />
 
 	  <div class="vertical-center">
 	    <span class="name-title">Alexander "PapaTutuWawa"</span>
@@ -39,12 +39,13 @@
 
 	<br />
 
-	<center class="footer">
+	<div class="horizontal-center footer">
 	  Created by <i>PapaTutuWawa</i> with &lt;3 using
 	  <a href="https://github.com/google/roboto">Roboto</a>,
 	  <a href="https://github.com/RedHatOfficial/Overpass">Overpass</a> and
 	  <a href="https://github.com/sunainapai/makesite">makesite</a>
-	</center>
+	</div>
+      </div>
     </div>
   </body>
 </html>

layout/templates/screenshot.html

@@ -1,5 +1,5 @@
 <div>
   <a href="https://{{ item.source_url }}" target="_blank">
-    <img class="screenshot clickable" src="{{ item.screenshot }}" />
+    <img class="screenshot clickable" src="{{ item.screenshot }}" alt="Screenshot of {{ item.title }}" />
   </a>
 </div>