diff --git a/404.html b/404.html
index 8d43bfd..5265312 100644
--- a/404.html
+++ b/404.html
@@ -131,6 +131,21 @@
             d.fx = null;
             d.fy = null;
         }
+
+        const disabledKeys = ["c", "C", "x", "J", "u", "I"]; // keys that will be disabled
+  const showAlert = e => {
+    e.preventDefault(); // preventing its default behaviour
+    return alert("Sorry, you can't view or copy source codes this way!");
+  }
+  document.addEventListener("contextmenu", e => {
+    showAlert(e); // calling showAlert() function on mouse right click
+  });
+  document.addEventListener("keydown", e => {
+    // calling showAlert() function, if the pressed key matched to disabled keys
+    if((e.ctrlKey && disabledKeys.includes(e.key)) || e.key === "F12") {
+      showAlert(e);
+    }
+  });
     </script>
     <p class="output">Please try to <a href="javascript:history.back()">go back</a> or <a href="/">return to the homepage</a>.</p>
 </body>