diff --git a/public/css/login.css b/public/css/login.css
index 16a68ad..1d697ce 100644
--- a/public/css/login.css
+++ b/public/css/login.css
@@ -163,3 +163,73 @@ button,
   border: none;
   box-sizing: border-box;
 }
+
+/* ── Error Popup ───────────────────────────────── */
+.login-overlay {
+  display: none;
+  position: fixed;
+  inset: 0;
+  background: rgba(0, 0, 0, 0.65);
+  z-index: 9998;
+}
+
+.login-popup {
+  display: none;
+  position: fixed;
+  top: 50%;
+  left: 50%;
+  transform: translate(-50%, -50%);
+  z-index: 9999;
+  width: 360px;
+  background: rgba(10, 15, 20, 0.95);
+  backdrop-filter: blur(10px);
+  border: 1px solid rgba(100, 170, 255, 0.4);
+  border-radius: 10px;
+  box-shadow:
+    0 0 40px rgba(0, 0, 0, 0.8),
+    0 0 20px rgba(70, 120, 255, 0.5);
+  font-family: "Tangerine", serif;
+}
+
+.login-popup-header {
+  padding: 14px 20px;
+  border-bottom: 1px solid rgba(100, 170, 255, 0.25);
+  display: flex;
+  align-items: center;
+  gap: 10px;
+  font-size: 26px;
+  color: #7dd3ff;
+}
+
+.login-popup-body {
+  padding: 20px;
+  font-size: 24px;
+  color: #ccc;
+  line-height: 1.5;
+}
+
+.login-popup-footer {
+  padding: 0 20px 18px;
+  display: flex;
+  justify-content: flex-end;
+}
+
+.login-popup-btn {
+  padding: 10px 28px;
+  font-size: 24px;
+  font-family: "Tangerine", serif;
+  background: linear-gradient(45deg, #3da2ff, #7dd3ff);
+  border: none;
+  border-radius: 6px;
+  color: #fff;
+  font-weight: bold;
+  cursor: pointer;
+  transition: 0.25s;
+  width: auto;
+  margin-bottom: 0;
+}
+
+.login-popup-btn:hover {
+  transform: scale(1.05);
+  box-shadow: 0 0 20px #4aa3ff, 0 0 40px #4aa3ff;
+}
diff --git a/views/index.ejs b/views/index.ejs
index 5aa6a34..ba75aa6 100644
--- a/views/index.ejs
+++ b/views/index.ejs
@@ -64,5 +64,25 @@
     </div>
 
   </div>
+
+  <% if (typeof error !== 'undefined' && error) { %>
+  <div class="login-overlay" id="login-overlay"></div>
+  <div class="login-popup" id="login-popup">
+    <div class="login-popup-header">
+      ⚔️ Hinweis
+    </div>
+    <div class="login-popup-body">
+      <%= error %>
+    </div>
+    <div class="login-popup-footer">
+      <button class="login-popup-btn" onclick="document.getElementById('login-popup').style.display='none';document.getElementById('login-overlay').style.display='none';">OK</button>
+    </div>
+  </div>
+  <script>
+    document.getElementById('login-overlay').style.display = 'block';
+    document.getElementById('login-popup').style.display = 'block';
+  </script>
+  <% } %>
+
 </body>
 </html>