Update app.css

app.css

@@ -65,12 +65,6 @@ h1 {
     text-decoration: underline;
 }
 
-/* Highlight dead links */
-.dead-link {
-    border: 2px solid #D32F2F; /* Red border */
-    background-color: #FFF9C4; /* Light yellow background */
-}
-
 @media screen and (max-width: 600px) {
     .card-content h3 {
         font-size: 1em;