Add details not found page

src/main/resources/static/details.html

@@ -19,7 +19,7 @@
         </aside>
     </template>
 
-    <main class="skeleton">
+    <main id="details" class="skeleton">
         <header data-id="dataset-id">
             <h1 id="title" data-type="api">Title</h1>
             <span>
@@ -41,7 +41,7 @@
             <a id="terms-of-use">Terms of Use</a>
         </section>
         
-        <section id="details">
+        <section>
             <p id="full-description">Full description<br>
                 Lorem ipsum dolor sit amet consectetur adipisicing elit. Beatae
                 nihil saepe et numquam quo id voluptatum recusandae assumenda
@@ -59,5 +59,18 @@
             </p>
         </section>
     </main>
+
+    <main id="not-found" class="hidden">
+        <h1>This is not the page you're looking for.</h1>
+        <div id="nothing-found-bg"></div>
+        <p>
+            The dataset or API you were sent to is not in our database.
+            Either it has been deleted by its author or we didn't know of it
+            to begin with.
+            <br>
+            You can try browsing for other datasets and APIs on our
+            <a href="/">homepage</a>.
+        </p>
+    </main>
 </body>
 </html>