diff --git a/src/app/not-found.tsx b/src/app/not-found.tsx
new file mode 100644
index 0000000..aea9093
--- /dev/null
+++ b/src/app/not-found.tsx
@@ -0,0 +1,57 @@
+import Link from "next/link";
+
+export default function NotFound() {
+  return (
+    <div className="min-h-[60vh] flex items-center justify-center">
+      <div className="text-center px-4">
+        <div className="mb-8">
+          <h1 className="text-8xl md:text-9xl font-bold font-vt323 text-cerulean-blue-500">404</h1>
+          <div className="mt-4 text-2xl md:text-3xl font-semibold text-gray-800">Page Not Found</div>
+        </div>
+
+        <p className="text-gray-600 text-base md:text-lg mb-8 max-w-md mx-auto">
+          The page you&apos;re looking for doesn&apos;t exist or has been moved.
+        </p>
+
+        <div className="flex flex-col sm:flex-row gap-4 justify-center items-center">
+          <Link
+            href="/"
+            className="bg-cerulean-blue-600 hover:bg-cerulean-blue-700 text-white py-3 px-6 rounded-md transition-colors font-medium"
+          >
+            Go to Home
+          </Link>
+        </div>
+
+        <div className="mt-12 pt-8 border-t border-gray-200">
+          <p className="text-sm text-gray-500 mb-4">Looking for something specific?</p>
+          <div className="flex flex-wrap gap-4 justify-center text-sm">
+            <Link
+              href="https://docs.sourcify.dev/docs/api/"
+              target="_blank"
+              rel="noopener noreferrer"
+              className="text-cerulean-blue-600 hover:text-cerulean-blue-700 hover:underline"
+            >
+              API Documentation
+            </Link>
+            <Link
+              href="https://sourcify.dev"
+              target="_blank"
+              rel="noopener noreferrer"
+              className="text-cerulean-blue-600 hover:text-cerulean-blue-700 hover:underline"
+            >
+              Sourcify Main Site
+            </Link>
+            <Link
+              href="https://github.com/sourcifyeth/4byte.sourcify.dev"
+              target="_blank"
+              rel="noopener noreferrer"
+              className="text-cerulean-blue-600 hover:text-cerulean-blue-700 hover:underline"
+            >
+              GitHub Repository
+            </Link>
+          </div>
+        </div>
+      </div>
+    </div>
+  );
+}
diff --git a/src/app/signatures/page.tsx b/src/app/signatures/page.tsx
new file mode 100644
index 0000000..baef458
--- /dev/null
+++ b/src/app/signatures/page.tsx
@@ -0,0 +1,5 @@
+import { redirect } from "next/navigation";
+
+export default function SignaturesPage() {
+  redirect("/");
+}
diff --git a/src/app/tools/abi/page.tsx b/src/app/tools/abi/page.tsx
new file mode 100644
index 0000000..7db0084
--- /dev/null
+++ b/src/app/tools/abi/page.tsx
@@ -0,0 +1,77 @@
+import Link from "next/link";
+import { FiExternalLink, FiArrowRight } from "react-icons/fi";
+import type { Metadata } from "next";
+
+export const metadata: Metadata = {
+  title: "ABI Decoder - 4byte.sourcify.dev",
+  description: "ABI decoder has moved to Swiss Knife calldata decoder",
+};
+
+export default function ABIDecoderPage() {
+  return (
+    <div className="min-h-[60vh] py-8">
+      <div className="max-w-3xl mx-auto">
+        <div className="bg-white rounded-lg shadow-lg border border-gray-200 p-6 md:p-8">
+          <div className="mb-6">
+            <h1 className="text-3xl md:text-4xl font-bold font-vt323 text-gray-800 mb-2">ABI Decoder</h1>
+            <p className="text-gray-600">Decode Ethereum calldata and transaction inputs</p>
+          </div>
+
+          <div className="bg-cerulean-blue-50 border border-cerulean-blue-200 rounded-lg p-6 mb-6">
+            <div className="flex items-start gap-3">
+              <div className="flex-shrink-0 mt-1">
+                <FiArrowRight className="w-6 h-6 text-cerulean-blue-600" />
+              </div>
+              <div>
+                <h2 className="text-lg font-semibold text-gray-800 mb-2">ABI Decoder Has Moved</h2>
+                <p className="text-gray-700 mb-4">
+                  We no longer maintain openchain.xyz&apos;s ABI decoder. Please use Swiss Knife&apos;s ABI decoder
+                  instead.
+                </p>
+                <a
+                  href="https://calldata.swiss-knife.xyz/decoder"
+                  target="_blank"
+                  rel="noopener"
+                  className="inline-flex items-center gap-2 bg-cerulean-blue-600 hover:bg-cerulean-blue-700 text-white py-3 px-6 rounded-md transition-colors font-medium"
+                >
+                  Go to Swiss Knife ABI Decoder
+                  <FiExternalLink className="w-4 h-4" />
+                </a>
+              </div>
+            </div>
+          </div>
+
+          <div className="border-t border-gray-200 pt-6">
+            <h3 className="text-lg font-semibold text-gray-800 mb-3">Other Resources</h3>
+            <div className="space-y-3">
+              <Link
+                href="/"
+                className="flex items-center gap-2 text-cerulean-blue-600 hover:text-cerulean-blue-700 hover:underline"
+              >
+                <FiArrowRight className="w-4 h-4" />
+                Search for function signatures
+              </Link>
+              <Link
+                href="/import"
+                className="flex items-center gap-2 text-cerulean-blue-600 hover:text-cerulean-blue-700 hover:underline"
+              >
+                <FiArrowRight className="w-4 h-4" />
+                Import/Submit signatures
+              </Link>
+              <Link
+                href="https://docs.sourcify.dev/docs/api/"
+                target="_blank"
+                rel="noopener noreferrer"
+                className="flex items-center gap-2 text-cerulean-blue-600 hover:text-cerulean-blue-700 hover:underline"
+              >
+                <FiArrowRight className="w-4 h-4" />
+                Sourcify API documentation
+                <FiExternalLink className="w-3 h-3" />
+              </Link>
+            </div>
+          </div>
+        </div>
+      </div>
+    </div>
+  );
+}
diff --git a/src/components/Header.tsx b/src/components/Header.tsx
index e7cab50..ea2d23e 100644
--- a/src/components/Header.tsx
+++ b/src/components/Header.tsx
@@ -69,7 +69,7 @@ export default function Header() {
   return (
     <>
       {/* Migration Banner */}
-      <div className="bg-cerulean-blue-600 text-white py-3 px-4 text-center">
+      <div className="bg-cerulean-blue-500 text-white py-3 px-4 text-center">
         <div className="max-w-[100rem] mx-auto">
           <p className="text-sm md:text-base">
             📢 <strong>Migration Notice:</strong> Sourcify is taking over{" "}