bg-card will be added to the class and password/username validation

bg-card should not be an id, ids should be unique in their use.

src/main/resources/templates/about.html

@@ -11,7 +11,7 @@
         <br><br>
         <div class="container">
           <div class="row justify-content-center">
-            <div class="col-md-6" id="bg-card"></div>
+            <div class="col-md-6 bg-card"></div>
           </div>
         </div>
       </div>