修改404.html文件

提升可读性、样式以及用户体验、添加导航链接提供返回首页的途径或者搜索功能能够帮助用户轻松回到正轨。我添加了一些基础的
CSS 样式，使 404
页面在视觉上更具辨识度。例如，为错误代码使用了更大的字号，采用了更醒目的颜色，并且确保链接能够突出显示且便于操作。

404.html

@@ -4,4 +4,36 @@
 permalink: /404.html
 ---
 
-<h1 class="title">404</h1>
+<div class="error-page">
+    <h1 class="title">404</h1>
+    <p>Sorry, the page you were looking for doesn't exist or has been moved.</p>
+    <p>You can go back to the <a href="/">home page</a> or use the search bar to find what you're looking for.</p>
+    <p>If you think this is an error, please contact us.</p>
+</div>
+
+<style>
+    .error-page {
+        text-align: center;
+        padding: 50px;
+        font-family: Arial, sans-serif;
+    }
+
+    .error-page .title {
+        font-size: 100px;
+        color: #ff6f61;
+    }
+
+    .error-page p {
+        font-size: 18px;
+        color: #333;
+    }
+
+    .error-page a {
+        color: #007bff;
+        text-decoration: none;
+    }
+
+    .error-page a:hover {
+        text-decoration: underline;
+    }
+</style>