diff --git a/lib/servez.js b/lib/servez.js
index 3cb8e66..ccde6ff 100644
--- a/lib/servez.js
+++ b/lib/servez.js
@@ -96,14 +96,37 @@ const noopLogger = {
   }),
 };
 
-function makeErrorHTML(msg) {
-  return `
-<style>
-:root {
-  color-scheme: light dark;
+function escapeStringForHTML(s) {
+  return s
+    .replaceAll('&', '&amp;')
+    .replaceAll('<', '&lt;')
+    .replaceAll('>', '&gt;');
 }
-</style>
-<pre>${msg}</pre>`;
+
+function makeErrorHTML(msg) {
+  return `\
+<!DOCTYPE html>
+<html>
+  <style>
+  :root {
+    color-scheme: light dark;
+  }
+  html, body, .msg {
+    height: 100%;
+    font-family: monospace;
+  }
+  .msg {
+    word-break: break-word;
+    display: flex;
+    justify-content: center;
+    align-items: center;
+  }
+  </style>
+  <body>
+    <div class="msg"><div>${escapeStringForHTML(msg)}</div></div>
+  </body>
+</html>
+`;
 }
 
 class Servez extends EventEmitter {
