diff --git a/web/server.go b/web/server.go
index 5e4814c..92386d9 100644
--- a/web/server.go
+++ b/web/server.go
@@ -931,21 +931,21 @@ func (s *Server) handleValidateCarNumber() http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
 		carNumber := r.URL.Query().Get("car_number")
 		if carNumber == "" {
-			http.Error(w, "<div class='alert alert-danger'>Car number is required</div>", http.StatusBadRequest)
+			http.Error(w, "<div class='invalid-feedback alert alert-danger'>Car number is required</div>", http.StatusBadRequest)
 			return
 		}
 
 		isUnique, err := s.db.IsCarNumberUnique(carNumber)
 		if err != nil {
 			s.logger.Error("Failed to check car number uniqueness", "error", err)
-			http.Error(w, "<div class='alert alert-danger'>Failed to validate car number</div>", http.StatusInternalServerError)
+			http.Error(w, "<div class='invalid-feedback alert alert-danger'>Failed to validate car number</div>", http.StatusInternalServerError)
 			return
 		}
 
 		if !isUnique {
-			w.Write([]byte("<div class='alert alert-danger'>Car number is already in use</div>"))
+			w.Write([]byte("<div class='invalid-feedback alert alert-danger'>Car number is already in use</div>"))
 		} else {
-			w.Write([]byte("<div class='alert alert-success'>Car number is available</div>"))
+			w.Write([]byte("<div class='invalid-feedback alert alert-success'>Car number is available</div>"))
 		}
 	}
 }