error message tweaks

_includes/layouts/index.njk

@@ -16,14 +16,14 @@ layout: page.njk
       <label for="name">Name <span class="red" aria-hidden="true">*</span></label>
       <input id="name" type="text" name="name" placeholder="Your Name"
         required aria-required="true" aria-describedby="name-error">
-      <p id="name-error" class="error">Name cannot be empty</p>
+      <p id="name-error" class="error">Name cannot be empty.</p>
     </div>
 
     <div class="form-field">
       <label for="email">Email <span class="red" aria-hidden="true">*</span></label>
       <input id="email" type="email" name="email" placeholder="you@example.com"
         required aria-required="true" aria-describedby="email-error">
-      <p id="email-error" class="error">Email cannot be empty</p>
+      <p id="email-error" class="error">Email cannot be empty and must be a valid email.</p>
     </div>
   </div>
 
@@ -31,7 +31,7 @@ layout: page.njk
     <label for="message">Message <span class="red" aria-hidden="true">*</span></label>
     <textarea id="message" name="message" rows="4" placeholder="What's your message?"
       required aria-required="true" aria-describedby="message-error"></textarea>
-    <p id="message-error" class="error">Message cannot be empty</p>
+    <p id="message-error" class="error">Message cannot be empty.</p>
   </div>
 
   <button type="submit" class="form-button">Send message</button>