Add code block warning

source/index.html.md

@@ -154,7 +154,7 @@ curl "http://example.com/api/kittens/2"
 
 This endpoint retrieves a specific kitten.
 
-<aside class="warning">If you're not using an administrator API key, note that some kittens will return 403 Forbidden if they are hidden for admins only.</aside>
+<aside class="warning">Inside HTML code blocks like this one, you can't use Markdown, so use <code>&lt;code&gt;</code> blocks to denote code.</aside>
 
 ### HTTP Request